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Chapter 21 – Pertussis vaccines Kathryn M. Edwards, Michael D. Decker

Introduction History of disease Pertussis (whooping cough) is a bacterial respiratory infection caused by Bordetella pertussis, a Gram-negative bacillus. Its major manifestation is a protracted cough illness that lasts many weeks, marked by characteristic intense paroxysmal coughing spells that often terminate in an inspiratory ‘whoop.’ The disease is most severe in infants and young children. The first known description of an outbreak of pertussis is that of Guillaume De Baillou, who described an epidemic that occurred in Paris in the summer of 1578.[1] This epidemic primarily affected infants and young children and resulted in high mortality. Apparently the disease had been known previously in France, because De Baillou referred to its common name of quinte, which he hypothesized might have reflected the characteristic sound of the cough or the 5-hour periodicity of the paroxysms. A disease known in Britain from the early 16th century as chyne- cough probably was pertussis, and the terms whooping cough and chincough appeared in the London Bills of Mortality in 1701.[2] The causative organism was first grown by Jules Bordet and Octave Gengou in 1906, and the first crude vaccines appeared soon thereafter.[3] Despite availability of acellular vaccines, whole-cell vaccines remain the most widely used globally. Whole-cell vaccines are produced locally in many regions of the world, are generally efficacious, and are inexpensive to produce.

Why the disease is important Prior to widespread use of whole-cell pertussis vaccine, there were as many as 270,000 cases of pertussis reported each year in the United States (indeed, the true case count likely approximated the annual birth cohort), with 10,000 deaths.[4] The occurrence of pertussis declined markedly after universal pertussis vaccination of children with whole-cell vaccine in the 1940s, to a nadir of 1,010 cases reported in 1976,[5] but has since progressively increased, with over 25,000 cases reported for 2004, the highest total since 1959.[6,7,7a,7b] The increase in pertussis in the United States has been greatest among older children and adults, probably reflecting waning vaccine-induced immunity and increasing appreciation of the disease in this age group. However, because pertussis still frequently goes undiagnosed in adolescents and adults, it is likely that the actual number of cases greatly exceeds the number reported. Recent reports also indicate that pertussis incidence continues to increase in infants too young to have received three doses of pertussis-containing vaccine.[6,7,7a,7b] During 2000–2004 an average of 2,488 cases of pertussis were reported annually in infants<1 year of age with 63% of them requiring hospitalization.[7]. Worldwide, pertussis remains an important problem in children. The World Health Organization (WHO) estimates that globally 45 million cases of pertussis occur annually, with 301,408 deaths reported in children for 2002.[8,9]

1 Background Clinical description

Infants and young children

The incubation period of pertussis averages 9 or 10 days (range, 6–20 days). The onset is insidious, and symptoms are indistinguishable from those of a minor upper respiratory infection. Fever is usually minimal throughout the course of infection. Cough initially intermittent, progresses within 1 or 2 weeks to become paroxysmal. The paroxysms increase in both frequency and severity and then gradually subside, rarely lasting longer than 2–6 weeks. In the absence of immunization, most children experience the full-blown disease; however, some children appear to develop either clinical immunity or serologic evidence of prior infection without a history of clinical pertussis, suggesting that mild atypical cases occur.[9,10] It is during the paroxysmal stage, when the cough is most severe, that the characteristic whoop occurs. The whoop is caused by forced inspiration through a narrowed glottis immediately after a paroxysm of a dozen or more rapid, short coughs without intervening inspiration. The characteristic whoop is seen less often in infants. The paroxysms may reflect difficulty in expelling thick mucus from the tracheobronchial tree, may be an effect of toxins, or both. During a paroxysm, cyanosis may occur and vomiting may ensue. The clinical picture of a young infant in a severe paroxysm is distressing indeed. After the episode, the child is often exhausted; unfortunately, several paroxysms may occur successively within a few minutes. Between paroxysms, the child may be playful and appear quite normal. Paroxysms may be induced by eating, laughing, crying, and a variety of other stimuli and are usually worse at night. In an infant with suspected pertussis, it is imperative that the clinician witness a paroxysm to ensure that apnea or respiratory arrest does not occur and that the child can be managed as an outpatient. Recovery is gradual. The paroxysms become less frequent and milder, and the whoop disappears. Nonparoxysmal cough may persist for many weeks during the convalescent phase, with intercurrent viral respiratory infections triggering recurrence of the paroxysmal cough. One of the largest studies to characterize the symptoms associated with pertussis in infants and children was conducted from October 1990 to September 1996 in Germany during active surveillance for a pertussis vaccine trial.[10] B. pertussis was isolated in 2,592 cases (age range, 6 days to 41 years); 50.7% were female. In unvaccinated patients, 90.2% had paroxysmal cough, 78.9% demonstrated whooping, 53.3% presented with posttussive vomiting and only 5.7% had fever ≥38° C. Leukocy-tosis and lymphocytosis were observed in 71.9% and 75.9% of unvaccinated patients, respectively.

Complications and sequelae in infants and children Minor complications of pertussis include subconjunctival hemorrhages and epistaxis secondary to the paroxysms, edema of the face, and ulcers of the lingual frenulum due to protrusion of the tongue during paroxysms. Suppurative otitis media frequently occurs (caused by the usual upper respiratory bacteria, such as Streptococcus pneumoniae or Haemophilus influenzae and not B. pertussis).

2 In the German study mentioned above, the overall rate of major complications in infants and children was 5.8%, with pneumonia seen in 29% of those with complications. In infants <6 months of age, the rate of complications was 23.8%.[10] Major complications can generally be grouped into three types: pulmonary, encephalitic, and nutritional. Of these, pulmonary complications are the most frequent.[10] The vast majority of full-blown pertussis cases exhibit some degree of atelectasis or bronchopneumonia. Pathologically, the pneumonia is both interstitial and alveolar, and the usual exudate is primarily mononuclear.[11] Pneumonic involvement may be sufficiently severe to compromise respiratory function and to cause death. In the past several years there has been an increasing appreciation for the role of pulmonary hypertension as an unexplained complication of pertussis in young infants.[12–20] Infants younger than 6 weeks of age with pulmonary hypertension have the highest mortality and autopsy findings reveal arterial thromboses. Infants with pertussis who fail artificial ventilation and are managed using extracorporeal membrane oxygenation (ECMO) have extremely high death rates (>80% in infants<6 weeks of age).[12] Generally children who survive pneumonia or pulmonary complications are not left with permanent lung damage.[21]

Acute pertussis encephalopathy, generally occurring during the paroxysmal stage, is characterized by seizures and altered consciousness and usually results from hypoxia or intracranial bleeding associated with paroxysmal cough. However, elevated cerebrospinal fluid levels of antibodies to PT and FHA were reported in one child with pertussis encephalopathy suggesting entry of the toxins into the brain.[22] In a series of infants hospitalized with pertussis in Canada; seizures were seen in 21% of fatal cases, but in none of the survivors.[23] Only limited data on the incidence of encephalopathy are available; estimates from population-based studies have ranged from 8 to 80 per 100,000 cases.[24,25] Of the cases reported to the Centers for Disease Control and Prevention (CDC) between 1997 and 2000, 26 (representing a population rate of 0.9 per 100,000) were complicated by ence-phalopathy.[6] Approximately one third of children with pertussis encephalopathy succumb to the acute illness, one third survive with permanent brain damage, and one third recover without obvious neurologic sequelae. [26] Nutritional deficiencies resulting from repeated vomiting can also be problematic. Inability to maintain adequate caloric intake in previously malnourished children who develop pertussis is a particularly severe problem in developing countries.

Adolescents and adults Pertussis also plays an important role in the etiology of cough illness in adolescents and adults (see below under Epidemiology). Recent CDC data indicate that of the 25,827 cases of pertussis reported during 2004, 8,897 (34%) occurred in adolescents aged 11–18 years, representing a population incidence of 30 per 100,000.[6,7] Furthermore, adolescents and adults have been demonstrated to be a reservoir for pertussis infection and serve as a source of spread to young children.[27–29] The clinical characteristics of pertussis in older adolescents and adults were highlighted in a large Canadian study.[30] Females comprised 71% of the reported cases. Reflecting the long history of pertussis vaccination in Canada, nearly 60% of the subjects reported prior pertussis vaccination, with less than 10% having prior natural infection. Subjects with confirmed pertussis had a median of 56 days of cough and 43 days with violent cough. Vomiting was seen in 46% of

3 the subjects, night cough in 84%, and apnea for 30 seconds after cough in 14%. Adults had higher rates of complications than adolescents, including pneumonia. German household contact studies conducted during active surveillance for pertussis vaccine trials also outlined the signs and symptoms of adult pertussis.[31,32] Of 79 German adults with symptomatic pertussis, 34% had been diagnosed with natural pertussis as children; 91% had cough with their present illness, 80% had cough lasting longer than 21 days, and one subject had a cough for 8 months.[32] Prolonged paroxysmal cough was experienced by 63%, cough resulting in sleep disturbance was reported in 52%, cough followed by vomiting occurred in 42%, and whoops occurred in 8%. The adults usually expectorated ‘a glassy, viscous mucus.’ Malaise was reported in 30% and arthralgia in 15%. Eleven patients reported attacks involving flushing and sweating. These episodes lasted 1–2 minutes, occurred several times a day, and continued for 2–8 weeks. Family studies of children with culture-confirmed pertussis disease and seroprevalence studies have both shown that asymptomatic infections are common in older children and adults.[33–35] Frequently, these asymptomatic adults have been implicated in the spread of infection to susceptible children. For example, in one study, four children with confirmed pertussis infection and their 18 family members were evaluated with culture and serology for B. pertussis. The attack rate for pertussis infection in contacts was 83%, but two thirds of the cases in immunized contacts were subclinical. All infected family contacts had elevated serologic tests for pertussis at the time the index case was diagnosed, but culture identified only 20% of the infected contacts. Symptomatic infection was characterized by a higher pertussis toxin (PT) antibody response and asymptomatic infection by a higher filamentous hemagglutinin (FHA) antibody response. These data suggest that, after pertussis immunization, immunity to disease is greater than is protection from infection.[35]

Complications and sequelae in adults Complications of pertussis were seen in 18 (23%) of the 79 adult patients in one study.[32] These included otitis media (four patients), pneumonia (two patients), urinary incontinence (three patients), rib fracture (one patient), and severe weight loss (one patient). In a recent CDC report of adolescent and adult pertussis, hospitalizations were seen in up to 2%, rib fracture and loss of consciousness in 1%, and seizures in 0.2%.[7] Other known complications of pertussis in adults include cough syncope, in which a prolonged coughing attack is followed by unconsciousness; triggering of migraines,[36] carotid artery dissection,[37] and loss of memory.[38–40] Death from pertussis is rare in adolescents and adults, but has been reported.[7,41]

Bacteriology Overview The causative agent of pertussis is Bordetella pertussis, a small, Gram-negative, pleomorphic bacillus. Although the organism was identified before the turn of the century in stained preparations of respiratory secretions from children with pertussis and from pathology specimens,[42] the organism was not recovered in culture until 1906 by Bordet and Gengou. [3] The culture medium originally employed, now called Bordet–Gengou medium, is still used in some clinical laboratories, although more complex synthetic media have been devised and are employed in many laboratories to grow this relatively fastidious organism.

4 Two closely related organisms in the genus Bordetella are B. parapertussis and B. bronchiseptica. The former is responsible for a pertussis-like syndrome in humans, which usually is less severe than pertussis. The latter produces respiratory illnesses in domestic animals. Because the DNA structures of these two organisms are essentially identical to that of B. pertussis, it may be that the three organisms are actually subspecies of the same bacterium.[43,44] Of all the Bordetella species, only B. pertussis synthesizes PT. Although the chromosomes of B. parapertussis and B. bronchiseptica contain the PT loci, they are transcriptionally silent because of defective promotors.[45] In their virulent phase, these three organisms all produce similar virulence factors.[46] Indeed, some have suggested that the curious absence of descriptions of pertussis before the 16th century may represent the adaptation of an animal organism to humans as recently as five centuries ago.[43] However, recent evidence suggests that the association of B. pertussis with humans may be more ancient than previously assumed.[47] A recently identified pertussis strain, Bordetella holmesii, has been associated with bacteremia, endocarditis, and respiratory illness, mainly in immuno-compromised patients.[48–51] Another Bordetella species, Bordetella hinzii, has been isolated from the blood of an AIDS patient and from the respiratory secretions of a patient with cystic fibrosis.[52,53] Although many of the biologic activities of B. pertussis had been recognized for some time, attempts to determine the components responsible for these various activities were unsuccessful for many years. However, when individual components of the organism were characterized, this led to an enhanced understanding of the pathogenesis of the disease and spurred development of purified component (acellular) vaccines. Bordetella pertussis has a marked tropism for and attaches strongly to ciliated epithelial cells of the respiratory tract.[54,55] The bacteria may be internalized by the epithelial cells but generally they do not penetrate submucosal cells or invade the bloodstream. However, toxins produced by the organism can enter the bloodstream and produce systemic effects. Bordetella pertussis antigens that have been incorporated in acellular vaccines, as well as other known components of the pertussis organism, are listed in Table 21-1.

Table 21-1 -- Key Components of the Bordetella pertussis Organism Component Biological Activity Pertussis Toxin A secreted exotoxin that induces lymphocytosis, sensitivity to histamine, pancreatic islet cell activation, and immune enhancement Filamentous Involved in attachment to ciliated respiratory epithelium Hemagglutinin Fimbriae Involved in attachment to ciliated respiratory epithelium Pertactin An outer membrane protein that promotes adhesion to ciliated respiratory epithelium BrkA An outer membrane protein that mediates adherence and resists complement Adenylate Cyclase Inhibits phagocytic function Endotoxin Contributes to fever and local reactions in animals and, probably, in humans Tracheal Cytotoxin Causes ciliary stasis and cytopathic effects on tracheal mucosa

5 Component Biological Activity Dermonecrotic or Heat- Causes dermal necrosis and vasoconstriction in animals Labile Toxin Adolescents and Adults with Prolonged Cough Illness (7–56 Days) Who Met Various Case Definitions for Laboratory Confirmation o r Evidence of Pertussis

Key components Pertussis toxin PT, previously termed lymphocytosis-promoting factor, is a major contributor to the pathogenesis of pertussis and is generally believed to play an important role in the induction of clinical immunity. PT is an oligomeric structure composed of five different subunits, S1 through S5 (Fig. 21-1). Structurally it belongs to the A-B class of bacterial toxins. The S1 component (A protomer) catalyzes the ADP ribosylation of GTP-binding regulatory proteins involved in signal transduction in the eukaryotic cell. The A protomer is largely responsible for the recognized biologic activities of PT, including promotion of lymphocytosis, stimulation of islet cells, [56] sensitization to histamines, clustering of Chinese hamster ovary cells and adjuvant properties. The B oligomer is a ring-shaped structure that consists of one copy each of subunits S2, S3, and S5 and two copies of S4. S5 serves to link the two dimers, S2-S4 and S3-S4.[57] The primary function of the B oligomer is to facilitate the attachment of PT to the ciliated cells of the respiratory tract.[58,59] However, the B oligomer does have some enzymatic activities, including hemagglutination and T-cell mitogenicity. The entire PT molecule is required for the majority of the enzymatic activities of the A protomer (the A protomer does not function in the absence of the B oligomer).[56,60] PT produced by different agglutinogen-type strains of B. pertussis appears to have a single biologic and serologic identity.[61] PT is not produced by B. parapertussis or B. bronchiseptica; although these organisms contain genes that encode for biologically active forms of PT, the relevant promoters are inactive and toxin is not produced. [62] PT appears to play several major roles in the pathogenesis of pertussis, although the precise mechanisms are not entirely clear. First, it facilitates the attachment of B. pertussis to ciliated respiratory cells. Second, it appears to contribute to cell toxicity. Third, it plays a role in enhancing respiratory tract colonization by inhibiting neutrophil migration and recruitment during the first week after infection and allowing pertussis organisms to avoid rapid antibody- mediated clearance. Thus, PT appears to have evolved a strategy to establish acute infection and extend the period of infectiousness, even in the face of antibody.[63–65] Interestingly, however, intravenous injection of substantial quantities of active PT into adult human volunteers caused no adverse effects.[66]

Figure 21-1 Diagrammatic representation of the pertussis toxin (see text).

PT is a strong immunogen. Antibodies to PT are associated with clinical immunity to pertussis, and many investigators believe these antibodies to be the most important (some, the sole) mediators of clinical protection.[67] In the laboratory, antibodies to PT protect mice after intracerebral challenge with live B. pertussis (the mouse protection test) or after aerosol challenge.[56,68] Challenging mice that have been actively immunized with subunits of PT or

6 passively immunized with monoclonal antibodies to various PT subunits have suggested that the entire molecule is required for optimum protection.[56,59,60,69] PT is chemically or genetically inactivated (toxoided) for incorporation into acellular pertussis vaccines.

Filamentous hemagglutinin FHA, a large, hairpin-shaped molecule, is synthesized as a 367-kDa precursor that is modified at both ends and cleaved to form the mature 220-kDa protein. In vitro studies suggest that FHA is an adhesin and has four separate binding domains that facilitate binding to monocytes and macrophages, ciliated respiratory epithelial cells, and nonciliated epithelial cells.[54] Data suggest that FHA may also have an immunomodulatory function. The interaction of FHA with receptors on macrophages suppresses the proinflammatory cytokine interleukin-12 via an interleukin-10- dependent mechanism and results in persistence of the organism by curbing the protective Th1 response.[70] Another study demonstrates that FHA stimulates proinflammatory and proapoptotic responses in human monocytes and respiratory epithelial cells.[71] Mutant organisms deficient in FHA adhere poorly in vitro.[54,72,73] Mice immunized with FHA are protected against lethal respiratory challenge with pertussis but not against intracerebral challenge.[68,74] FHA is a strong immunogen, and serum antibodies to FHA are found after natural infection and after immunization with vaccines containing this protein. The results of one epidemiologic study in Finland suggested that antibodies to FHA in immunized schoolchildren correlated with protection against pertussis disease (correlates of protection are discussed more fully in a subsequent section).[75]

Fimbriae and agglutinins Bordetella organisms express filamentous, polymeric, protein cell-surface structures called fimbriae. More than a dozen agglutinogens are present on the cell envelope of the three species of the genus bordetella; two of the known agglutinogens are fimbriae. Accordingly, the terms fimbriae and agglutinogens should not be considered synonymous, and should not be used interchangeably. Agglutinogen patterns differ among the three species. As many as eight are found in B. pertussis, six of which are unique to that species, but only agglutinogens 1, 2, and 3 are considered to be of importance in disease pathogenesis and immunity. Antibodies to these agglutinogens have been useful in seroepidemiologic studies. In vivo studies have shown that fimbriae-negative strains of B. pertussis are defective in their ability to multiply in the nasopharynx and trachea of mice.[76] B. bronchiseptica strains devoid of fimbriae but unaltered in expression of FHA and other putative adhesins are unable to colonize animal trachea. [77]Serum antibodies to the fimbriae are found almost universally after natural disease or after immunization with vaccines containing these proteins. There is accumulating evidence regarding the role of antibodies to agglutinogens in clinical immunity. Data supporting such a role are that the efficacy of whole-cell pertussis vaccines appeared to be compromised in the absence of a ‘match’ between the agglutinogens in the vaccine and those of prevalent B. pertussis strains. There is some in vitro evidence of shifts in serotypes of B. pertussis on serial culture.[78] There is also evidence that a change in serotype occurs during the course of clinical pertussis in some instances.[79] Seroepidemiologic data from the United Kingdom indicated that, between 1941 and 1953, the circulating strains of B. pertussis contained agglutinogens 1, 2, and 3. By 1968, however, 75% of isolated strains contained only agglutinogens 1 and 3.[80] There is

7 suggestive evidence (but no proof) that this change resulted from the use of vaccines that contained relatively little agglutinogen 3.[79,81,82] One product that contained considerable agglutinogen 3 was far more effective than the others in preventing pertussis during this time. Subsequent manufacturing changes that incorporated more agglutinogen 3 resulted in higher efficacy.[79] It is, of course, possible that serotype differences are markers for some other antigenic differences in strains of B. pertussis; however, the biologic activities of PT from different serotypes of B. pertussis do not appear to differ.[61] Antibody to FIM appears to be strongly correlated with protection from clinical disease, based on the results of household contact studies among humans,[83] mouse model studies,[84] and in- vitro investigations.[85] Because of the evidence that the agglutinogens play some role in the induction of clinical immunity to pertussis, the WHO has recommended that whole-cell pertussis vaccines contain agglutinogens 1, 2, and 3.[86]

Pertactin Pertactin (PRN), originally known as the 69-kDa protein, is a surface-associated protein that is exported to the outer membrane, where it undergoes proteolytic cleavage.[87] Similar proteins are produced by B. parapertussis and B. bronchiseptica.[88] PRN participates in attachment through its Arg-Gly-Asp (RGD) motif to facilitate eukaryotic cell binding[88–90] and invasion.[91] PRN is highly immunogenic. Antibodies to PRN are found after natural disease or immunization with vaccines containing this protein.[92,93] Mice that have been protected passively with antibodies to PRN are highly resistant to an otherwise fatal aerosol challenge with virulent B. pertussis.[94]However, in the intracerebral mouse protection test, mice immunized with PRN are protected only when also immunized with FHA.[88] Studies from the Netherlands have shown that genetic variation in PRN (and PT) molecules exists, with a shift over time in the circulating strains toward variants not represented in the pertussis vaccine(s) used in the community.[95] Subsequent mouse-model studies have shown that the Dutch whole-cell pertussis vaccine is less effective against some PRN variants than others. In contrast, a study from France indicates that, despite lyophilization, multiple Sanofi Pasteur whole-cell vaccine lots stored since 1984 had conserved genomes and still expressed the major toxins and adhesins.[96] Studies from the same investigators confirmed that the vaccine lots were highly immunogenic in mice.[97] Additional studies from other geographic areas have been performed to determine whether selection pressure may have contributed to variation in the PRN molecule, leading to less effective vaccines.[98,99] A recent study from Sweden evaluating pertussis strains from 1970–2003 suggests that there is no evidence that there has been a reduction in the effectiveness of the vaccination program from bacterial polymorphism.[100] Although it is not known whether such variation might be seen with acellular vaccines, the presence of high concentrations of multiple antigens may decrease the likelihood of changes occurring in the PRN molecule, although this will need to be evaluated over time. Thus far, the available clinical[101,102] and experimental[103,104] data do not show reduced effectiveness of current diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccines against variant strains.

Adenylate cyclase

8 Adenylate cyclase, present in all virulent strains of B. pertussis, is synthesized as a protoxin monomer that is cleaved into an active molecule, which allows it to enter a variety of eukaryotic cells. Once inside the cell, it is activated by calmodulin and catalyzes the production of large quantities of cyclic AMP. Purified adenylate cyclase inhibits chemotaxis, chemiluminescence, and superoxide anion generation by monocytes and neutrophils in vitro, and in vivo augments production within the phagocyte of cyclic AMP from ATP, resulting in an excessive accumulation of cyclic AMP and paralysis of the various phagocytic functions. [46,105] Recent studies have shown that macrophage cyto-toxicity may also result from the induction of apoptosis and not solely from accumulation of cyclic AMP.[106] In vivo studies have shown that, compared to wild-type organisms, mutants in adenylate cyclase are defective in their ability to cause lethal infection. These findings suggest that adenylate cyclase serves as an anti-inflammatory and antiphagocytic factor during infection. In the mouse model of aerosol infection, PT and adenylate cyclase appear to be the two most important virulence factors. [107] Adenylate cyclase is immunogenic;[108] in mouse models of intracerebral and aerosol challenge, prior active immunization with adenylate cyclase was shown to be similar in protective efficacy to whole-cell vaccine.[109] In addition, it has been shown that adenylate cyclase antibodies interfere with the multiplication of organisms in these models.[109] Tracheal cytotoxin Of the virulence factors produced by Bordetella organisms, only tracheal cytotoxin induces paralysis and destruction of respiratory ciliated epithelium, the hallmark of the disease. Tracheal cytotoxin is a fragment released from the peptidoglycan of the B. pertussis cell wall. [110–112] Its activities were studied in vitro in tracheal organ and cell cultures and found to induce mitochondrial bloating, disruption of the tight junctions, extrusion of the ciliated epithelial cells, and little or no damage to the nonciliated cells.[46] There is also evidence to suggest that the cyto-pathology is due to tracheal cytotoxin's increasing production of nitric oxide that diffuses into ciliated cells, causing cell death. Heat-labile toxin Heat-labile toxin, so called because it is inactivated at 56°C, is also known as the dermonecrotic or mouse-lethal toxin because of its effects in experimental animals.[113] It is produced by all virulent Bordetella species. Located intracellularly, it can be recovered by disruption of B. pertussiscells. The mechanism of production of cutaneous lesions after injection of the toxin in animals appears to be vasoconstriction.[114] The toxin is lethal to mice when injected intravenously. The role, if any, of heat-labile toxin in the pathogenesis of pertussis is unknown. No consistent effects on cells have been recognized in vitro. It is a weak immunogen, antibodies to it are nonprotective in animal challenge tests, and its absence does not diminish the lethality of experimental pertussis infection in mice.[107] BrkA BrkA (Bordetella resistance to killing genetic locus, frame A), another outer membrane protein of B. pertussis similar in structure to PRN, protects the bacterium against classical-pathway complement-mediated killing.[115,116] It has been shown that antibodies to BrkA augment killing of B. pertussis.[117] Although increased susceptibility to complement during acute bacterial growth would seem to mark the organism for elimination, antibody is needed for classical complement activation. Antibody after a primary infection takes some time to develop and rapid multiplication might arise before killing could occur. In contrast to the primary infection, if

9 antibody has already been stimulated by natural disease or vaccine, a secondary response can be generated rapidly and killing might occur. This may explain why pertussis tends to be a milder disease after vaccination or after earlier natural infection.[118] Endotoxin The endotoxin or lipopolysaccharide of B. pertussis exhibits many of the in vivo activities of endotoxins produced by other Gram-negative organisms, but its role in pathogenesis or in recovery is unclear.[119] Organisms with incomplete endotoxin production have shown decreased colonization of the respiratory tract in the mouse model.[120] The endotoxin content of whole-cell vaccines may have contributed to the immediate adverse systemic and local reactions to those vaccines.[121]

Pathogenesis of pertussis Current knowledge of the components of B. pertussis and their actions permits construction of a reasonable hypothesis regarding the pathogenesis of whooping cough in humans. [46,122,123] Transmission occurs when airborne bacteria from symptomatic patients reach the ciliated respiratory epithelium of a susceptible host. Bordetella pertussis overcomes the mucosal immune defenses of the upper respiratory tract and causes disease in healthy individuals. The organisms attach strongly to the ciliated cells through several adhesins. Although PT and FHA are important attachment proteins, fimbrial proteins, PRN, and BrkA participate in this process as well.[55,72,87,123,124] The bacteria normally do not invade beyond the epithelial layers of the respiratory tract, but PT enters the bloodstream and exerts its biologic effects on systemic sites. PT, adenylate cyclase, and BrkA have marked effects on host immune function.[55,105,115,125] Adenylate cyclase induces production of high levels of cyclic AMP, disrupting the functions of several cell types of the immune system; PT inhibits chemotaxis of phagocytic cells into the site of inflammation; and BrkA protects the bacteria against classical complement attack.[115] Tracheal cytotoxin and heat-labile toxin are likely involved in the damage to the tracheobronchial epithelium that is so characteristic of the disease.[111–113] Although this sequence may explain the respiratory manifestations of pertussis, the pathogenesis of the encephalopathy that can complicate clinical disease remains unclear. [126] Suggested pathogenic mechanisms have included anoxia secondary to severe paroxysms, metabolic disturbances, hypoglycemia, minute intracranial hemorrhages;[126] or a direct toxic effect on the brain.[22]

Diagnosis The etiologic agent responsible for an infectious disease is generally determined by culture of the organism, detection of antigens or nucleic acids produced by the organism, or measurement of the immune response to the organism. Even when using all these criteria, the confirmation of B. pertussis infection is still one of the most difficult diagnostic challenges facing the clinician, particularly in adolescents and adults. Pertussis organisms typically can be detected in the nasopharynx of patients with pertussis only early in the illness, when the symptoms are similar to those of the common cold. By the time severe cough appears, the organisms typically have decreased in number or disappeared from the nasopharynx, making culture or antigen detection extremely difficult.

10 Bacteriologic diagnoses Culture Culture of B. pertussis from the nasopharynx of symptomatic patients is compelling evidence of disease and remains the ‘gold standard’ for laboratory diagnosis.[127,128] The greatest likelihood of isolating the organism is achieved by immediate inoculation of a nasopharyngeal aspirate specimen obtained early in the illness onto fresh media in a laboratory experienced with handling B. pertussis. At best, these conditions are difficult to meet, but, even under optimum circumstances, the organism is frequently not recovered because of its fastidious nature and its disappearance early in the disease process.[129] Cultures obtained after 21 days of cough are significantly less likely to yield organisms.[130–133] Because the human nasopharynx is colonized with many respiratory bacteria, the use of selective media containing antibiotics such as cloxacillin and cephalexin may increase the yield of positive pertussis cultures by suppressing normal flora and allowing Bordetella to grow.[131] Two media are specialized for pertussis cultures: Bordet–Gengou medium, containing defibrinated horse blood and cloxacillin; and Regan–Lowe medium, containing charcoal agar, defibrinated horse blood, and cephalexin. Granstrom and colleagues found that the two media detected comparable numbers of positive cultures in symptomatic unimmunized children with pertussis,[134] but others have reported better yield with Regan–Lowe medium.[131] Direct plating of the specimen at the bedside or clinic has also been shown to increase the yield of positive cultures, whereas prior therapy with erythromycin or sulfamethoxazole reduces the likelihood of positive cultures. Data from pertussis vaccine efficacy studies suggest that immunized individuals with pertussis have lower rates of positive cultures than unimmunized control subjects and that isolation rates are negatively correlated with increasing age.[135] This complicates the diagnosis of pertussis in partially or fully immunized adolescents or adults. In preparation for the Swedish efficacy trials of the acellular vaccines, investigators evaluated the parameters associated with optimal culture yields.[128] They concluded that nasopharyngeal aspirates yielded better samples than nasopharyngeal swabs and when swabs were used, Dacron was better than calcium alginate since the latter inhibited polymerase chain reaction (PCR) assays. Cotton was shown to be toxic to the bacteria. Aspirates were obtained by placing an infant feeding tube through the nose into the posterior pharynx, aspirating, removing the tube, and flushing it with 1 mL of normal saline. Although direct plating of the aspirate was optimal, if that was not possible, Regan–Lowe transport medium could be used if plated by 72 hours after inoculation. This enrichment process increased the number of positive cultures from 7 to 14%.[133] They also concluded that incubation for at least 7 days increased the yield. However, in spite of these refinements to increase the sensitivity of culture, they concluded that “Although the culture is the ‘gold standard’ for the diagnosis of pertussis, its position should be reconsidered, as the diagnostic sensitivity is insufficient even when technical conditions are optimal.”[128] Antigen detection: direct fluorescent antibody test and polymerase chain reaction Antigen detection tests offer the distinct advantage that organisms do not have to be viable for detection and therefore can be detected later in the disease and in the presence of antibiotics. The initial antigen detection test was the direct fluorescent antibody (DFA) test. Previous studies of DFA in experienced laboratories have shown a specificity of as high as 99.6% but a sensitivity of only 61% when compared with culture.[128,131,132,136] When properly performed, the

11 DFA test can provide a useful addition to culture and serology, particularly for the confirmation of clinically suspected cases. However, as with any diagnostic test, the positive predictive value of the test can be quite low when the true prevalence of disease is low. The replacement of polyclonal with monoclonal DFA reagents has been reported to enhance the assay performance but new detection methods have largely replaced the DFA.[137] More recently, PCR assays have been developed for the identification of unique gene sequences of B. pertussis in respiratory secretions.[131,138–143]Although bacteria can no longer be cultured after 5 days of therapy, the PCR can remain positive for an additional week. [144] Although still rather labor intensive and demanding of scrupulous technique to avoid cross- contamination, this rapid, highly sensitive and specific diagnostic method is steadily becoming more widely available. Improved techniques, such as immunomagnetic and solid-phase detection methods, offer the promise that a single organism might be detected with this improved technology in the years ahead. Two types of clinical samples have been tested in PCR assays: nasopharyngeal aspirates and nasopharyngeal swab specimens. During the investigation of pertussis epidemics, most studies have demonstrated that the PCR assay is more sensitive than culture in the diagnosis of pertussis and that nasopharyngeal swabs provide adequate samples for analysis. Several PCR assays have been developed, the majority of which target one of four chromosomal regions of the organism for amplification: (1) the PT promoter region, (2) repeated insertion sequences, (3) a region upstream from the porin gene, and (4) the adenylate cyclase toxin gene. Some have suggested that assays with repeated insertion sequences as the target are more sensitive with a low number of amplification cycles, but there also is an increased risk for cross-reaction with other species. A comparative trial examined the nationwide use of a PCR assay in Finland and Switzerland from nearly 4,000 clinical samples and found that the sensitivity of the PT promoter-based PCR was higher than that of the insertion sequence-based PCR.[145,146] In these studies, the PCR remained positive longer than culture and offered results more rapidly. Bordetella pertussis cultures typically take 3–7 days to become positive, whereas PCR can be completed more rapidly.[145] The various acellular pertussis vaccine efficacy trials conducted in the 1990s (see below) have provided information about the sensitivity and specificity of various PCR methods. In the Erlangen trial, 392 symptomatic subjects had nasopharyngeal samples for PCR compared with culture and serology. PCR and culture were positive in 22% and 6% of the samples, respectively. When serologic criteria were the gold standard, the sensitivity of the PCR was 61% and the specificity was 88%.[136] In another study conducted in Germany, 7,153 samples were taken from symptomatic children. Bordetella pertussis was identified by culture in 3% and by PCR in 7.6%, a 2.6-fold increase.[147] Studies by Swedish investigators have shown that rates of PCR positivity increased from 87.5 to 95% when aspirates were treated with cation-exchange resins. Overall, PCR increased the yield of positive samples by 38.6%.[128] Reports of the successful use of PCR in clinical laboratories and of the development of ‘real- time’ methods for the diagnosis of pertussis infections are encouraging and suggest that the diagnosis of pertussis infections may become easier for the clinician in the years ahead.[127,148– 153] However, the increased use of PCR must be coupled with rigorous quality assessment programs. Two recent reports serve to highlight this point. First, an evaluation of PCR assays routinely performed in diagnostic laboratories in Europe demonstrated that the choice of the target gene was particularly critical for species specificity of B. pertussis and that laboratories

12 varied in their accuracy of detection.[154] Second, two outbreaks of respiratory tract illness associated with prolonged cough were investigated in New York State. When 680 positive PCR samples detected in a private commercial laboratory were compared with results from the New York State Department of Health reference laboratory, a substantial number of PCR results were determined to be falsely positive. These examples highlight the importance of appropriate clinical laboratory quality assurance programs and the need for caution when interpreting positive PCR tests.[155] A further issue is the potential role of ‘clinical false positives.’ It has been shown that PCR is able to detect B. pertussis among persons exposed in an outbreak who do not have clinical evidence of pertussis disease.[156–158] Accordingly, it is important that categorization be based on appropriate clinical case definitions, and not merely on PCR positivity.

Serologic diagnosis Serologic tests for antibodies to various components of the B. pertussis organism have been used extensively in the research environment for the diagnosis of pertussis in children, and particularly, in adolescents and adults.[128,131,136,159–161] Serologic testing avoids the lack of sensitivity and other known limitations of culture methods and has improved our understanding of the clinical spectrum of pertussis, particularly by demonstrating asymptomatic, mild, or atypical infections in partially immune individuals.[35,162–164] Also serologic studies have been used to examine the natural history of pertussis in unimmunized populations by determining the prevalence of antibodies at various ages,[165–168] and they have been shown to be useful in monitoring the incidence of pertussis during regional outbreaks.[169] They have also been helpful in monitoring clinical outcomes in trials of newer pertussis vaccines, because partially immune individuals may incur pertussis infection but display few or no symptoms. [135] Finally, serologic studies have enabled an understanding of the role of pertussis in the etiology of cough illness in adolescents and adults.[170,171] Tests used to measure serum antibodies to B. pertussis include complement fixation, agglutination tests, toxin neutralization, and enzyme-linked immunosorbent assays (ELISAs).[131] Of these tests, ELISA methods are used most frequently because they are the easiest to perform and standardize and they can detect specific immunoglobulin isotype responses. Another advantage of the ELISA method is that serum antibodies against specific antigens of B. pertussis can be readily measured; for example, antibodies to PT and FHA are among those commonly assayed. Considerable effort has been expended to develop a standardized ELISA method that can be used in the evaluation of vaccine candidates and in the diagnosis of pertussis disease.[172–174] Methods of quantitation of antibody have also been refined.[175] Standardization has been important for the evaluation of vaccine candidates, but has not resulted in the widespread availability of serologic tests for the diagnosis of pertussis in most clinical laboratories. The diagnosis of a case of pertussis based on serology is dependent on the definition used. The most conclusive serologic evidence of an infection is the demonstration of a significant rise in specific antibodies as a consequence of the infection. Serologic definitions of many infectious diseases are made by fourfold titer rises between the pre- and the postimmunization samples. However, pertussis presents a problem because the diagnosis is often not considered early in the course of the disease. By this time, a substantial rise in serum antibodies has already occurred, thus compromising the likelihood of a significant increase between the acute and convalescent serum specimens. Indeed, the delay in

13 clinical suspicion and thus in obtaining the acute specimen may result in higher antibody levels in the acute than in the convalescent specimen; it has been demonstrated that fourfold decreases in antibody between the acute and convalescent spe-cimens can also be associated with culture-confirmed pertussis.[161] An approach that avoids this problem of specimen timing has been taken in studies of individuals with respiratory illnesses suspected to be pertussis.[162– 165] In these studies, the range of antibody levels is determined in a comparable control population not suspected to have pertussis. The distribution of antibody levels in single specimens from the population under investigation is determined and compared with that of the normal population. Those subjects whose antibody levels, singly or in various combinations, exceed the mean of the control population by a selected factor (typically, 2 or 3 standard deviations) are assumed to have experienced recent infection.[165,176–179] The strong influence of case definition on the number of subjects diagnosed with pertussis and on the estimates of pertussis disease prevalence is shown in Table 21-2. In this study, Senzilet et al. enrolled patients 12 years of age or older with persistent cough of 1–8 weeks’ duration from nine health units in eight Canadian provinces. Only two cases were diagnosed with positive culture, and three additional cases were detected with PCR. When serologic measures were used, only seven had a fourfold rise in titer between the acute and convalescent samples. However, 36 persons had a single antibody titer that exceeded the 99.9th percentile for controls, and 84 had single antibody titers that exceeded 3 standard deviations from that of the control subjects. As shown in Table 21-2, the calculated prevalence of pertussis disease in this population was highly dependent on the serologic definition.[28]

Table 21-2 -- Adolescents and Adults with Prolonged Cough Illness (7-56 Days) Who Met Various Case Definitions for Laboratory Confirmation o r Evidence of Pertussis Case No. positive/no. Prevalence, Mean age, definition Criteria tested %(95% CI) years (range) 1 Culture positive for Bordetella 2/440 0.5 (0.1–1.8) 18.4 (12.6– pertussis 24.1) 2 PCR positive for B. pertussis 3/314 1.0 (0.2–3.0) 24.0 (12.6– 37.8) 3 4-fold increase in antibody titer 7/393 1.8 (0.8–3.8) 28.1 (12.3– 70.6) 4 Antibody titer >99.99 percentile 36/440 8.3 (5.9–11.2) 36.6 (14.1– for control values 69.4) 5 Antibody titer >3 SDs greater than 84/440 19.1 (15.6–23.0) 39.0 (12.3– GMT for control subjects 87.7) Adapted from Senzilet LD, Halperin SA, Spika JS, et al. Pertussis is a frequent cause of prolonged cough illness in adults and adolescents. Clin Infect Dis 2001;32:1691–1697.

For many years, the Massachusetts Department of Public Health Laboratory has provided a single-sample pertussis serology assay with a specific cut-off value to diagnose pertussis in adolescents and adults. This system has contributed greatly to our understanding of the burden

14 of disease in that state. It is also noteworthy that the reported rates of pertussis in this population are 13-fold higher than in the rest of the United States, likely reflecting improved disease detection.[176] In an attempt to establish a standardized serologic test for pertussis and to make it routinely available to clinicians, the CDC funded a study to examine the distribution of immunoglobulin G (IgG) levels against three Bordetella pertussis antigens (pertussis toxin [PT], filamentous hemagglutinin [FHA], and fimbria types 2 and 3 [FIM]) and to determine population-based antibody levels for the purpose of establishing diagnostic cutoff points. Enzyme-linked immunosorbent assays (ELISAs) were performed on sera from >6000 U.S. residents aged 6–49 years who participated in the Third National Health and Nutrition Examination Survey. Mixture models were developed to identify hypothesized exposure groups and establish diagnostic cutoffs. Quantifiable (>20 ELISA units/ml (EU)) anti-FHA and anti-FIM IgG antibodies were common (65% and 62% of individuals, respectively), but quantifiable anti-PT IgG antibodies were less frequent (16%). Given the distributions of antibody levels, an anti-PT IgG level of >94EU was proposed as the diagnostic cutoff point. Application of this cutoff point to culture- confirmed pertussis in a prior study investigating cough illness yielded a high diagnostic sensitivity (80%) and specificity (93%). The PT cutoff point will be further evaluated in prospective studies of B. pertussis infection in adolescents and adults to confirm its utility.[168] A somewhat different problem is presented by the use of serologic testing to detect pertussis in field trials of pertussis vaccine. As mentioned above, the laboratory routine used and the criteria applied for serologic case confirmation in vaccine efficacy trials have a direct influence on the identification of cases, which consequently may also affect the estimation of vaccine efficacy. Some differences in the application of serologic confirmation criteria among the clinical studies of acellular pertussis vaccines include the level of increase in titer required and the use of single-specimen diagnostics. Additionally, the availability of pre-exposure serum specimens increases the sensitivity of serologic confirmation. In the 1992–1995 Stockholm trial, a regimen was introduced to collect serum samples systematically; using acute- and convalescent-phase sera from the cough episodes, the proportion of all cases that was serologically confirmed was 25%. When pre-exposure sera also were available, the proportion was 35%; the change in sensitivity was differential by vaccine group and thus had some effect on the calculation of vaccine efficacy. Therefore, given the different application of serologic methods among the various efficacy studies, direct comparisons of efficacy rates between these studies should be made with caution.[180] Another concern with serologic diagnosis is that, although it may be appropriate for nonimmunized control subjects, detection of antibody increases may be compromised in those who were recently immunized, because immunization itself leads to increases in antibody titer. In this situation, the evaluation of antibodies against an antigen of B. pertussis that was not included in the vaccine can be useful, if such an antigen exists.

Treatment and prevention with antibiotics New guidelines for the treatment and postexposure prophylaxis of pertussis have been issued and clarify the role of antibiotics in pertussis control.[181]The central tenet of the guidelines is that antibiotic treatment of pertussis and judicious use of antimicrobial agents for postexposure

15 prophylaxis will eradicate B. pertussis from the nasopharynx of symptomatic or asymptomatic persons. In addition, the administration of macrolides early in the course of illness will reduce the duration and severity of symptoms and lessen the infectivity.[4,182–190] Although many with untreated pertussis will spontaneously clear B. pertussis by 3–4 weeks after the onset of cough, untreated and unvaccinated infants can remain culture-positive for longer then 6 weeks. [191,192] Erythromycin, a macrolide antibiotic, has been the antimicrobial of choice for many years, but the unpleasant gastrointestinal side effects and the availability of newer antimicrobial agents have supported therapeutic changes. In vitro studies have documented the effectiveness of azithromycin and clarithromycin, with a reduction in side effects.[193–195] For the treatment of pertussis, erythromycin, clarithromycin, or azithromycin can be used in persons aged >1 month. However, because of the association of erythromycin and infantile pyloric stenosis, infants aged <1 month should receive azithromycin.[196,197] In those with intolerance to the macrolides, trimethoprim-sulfamethoxazole (TMP–SMZ) is the alternative agent. For post-exposure prophylaxis of close contacts of a person with pertussis, macrolides also are the agents of choice. Whether to administer postexposure chemoprophylaxis should be determined on the basis of the infectiousness of the patient, the duration and intensity of the exposure, the consequences of pertussis in the exposed individual, and the possibility of contact with persons at high risk for severe pertussis, such as young infants. Postexposure prophylaxis given to asymptomatic household contacts within 21 days of onset of cough in the index patient can prevent symptomatic infection. Symptomatic contacts should be treated as if they have pertussis. Postexposure prophylaxis also should be administered in exposure settings that include infants aged <12 months or women in the third trimester of pregnancy. For either therapy or prophylaxis, infants less than 1 month of age should receive azithromycin at a single dose of 10 mg/kg per day given for 5 days. In child-ren older than 1 month, treatment should consist of either azithromycin at the above dosage; erythromycin at a dosage of 40–50 mg/kg/day given every 6 hours for 14 days; or clarithromycin at a dosage of 15 mg/kg per day in two divided doses for 7 days. Adults also should receive either azithromycin at 500 mg on day one and then 250 mg for the next four days; erythromycin at a dosage of 2 grams per day given every 6 hours for 14 days; or clarithromycin at a dosage of 1 gram per day in two divided doses for 7 days.[182,186–189,198] If macrolides are not tolerated, trimethoprim-sulfamethoxazole (8 mg of trimethoprim/kg/day in two divided doses) has been recommended, although few data exist to confirm its efficacy.[186] One final concern with the use of macrolides, and particularly erythromycin, is the increasing prevalence of antibiotic resistance. Erythromycin resistance was first recognized in Arizona in 1994.[198] Since then, additional erythromycin-resistant isolates have been reported and new mutations described.[199–201] Screening of isolates from around the United States suggests that the rates of erythromycin resistance remain very low, but reports of a novel resistance phenotype that appears only after a 7-day incubation period suggest that clinicians should remain alert to potential treatment failures.[202] In summary, macrolides are recommended for both therapy and prophylaxis of household and other close contacts, regardless of vaccination status, and for healthcare workers with a high risk of, or known, exposure to pertussis.[203–205] Prophylaxis reduces, but does not eliminate, the risk of pertussis. [206,207] Prophylaxis within a household is substantially more effective if given before the appearance of the first secondary case.[207] Cases and inadequately vaccinated contacts younger

16 than 7 years of age should be excluded from school, day care, and similar settings until they have received at least 5 days of prophylaxis or therapy.[203]

Results of vaccination: whole-cell pertussis vaccines

Overview Although some observers have challenged whole-cell pertussis vaccine as being ineffective, dangerous, or superfluous,[276,277] most authorities agree that the widespread use of the vaccine has had enormous benefits.[185,278,279] Observations that have led to this conclusion include the results of clinical trials; the rapid decline in morbidity and mortality from pertussis concomitant with the implementation of whole-cell vaccine programs; the recurrence of disease in countries in which pertussis immunization has been discontinued, rates of acceptance have declined markedly, or vaccines have become ineffective; the inverse correlation of the pertussis attack rate with the proportion of immunized children in communities in which pertussis becomes epidemic; and the lower attack rates in previously immunized children than in unimmunized children under both endemic and epidemic conditions.

Immune responses to whole-cell vaccines Many of the world's children are immunized with whole-cell pertussis vaccines produced locally. Few data exist that compare the safety, immunogenicity, and efficacy of individual whole-cell products produced in various countries. Most authorities had presumed that all whole-cell vaccines were very similar and that one was as immunogenic and effective as another. However, when significant differences in immune responses were noted with whole- cell pertussis products produced by different manufacturers in the United States and Canada, it became apparent that all whole-cell vaccines were not the same.[226,280,281] The European acellular pertussis vaccine efficacy trials, using whole-cell vaccines produced in several different countries, demonstrated substantial differences in efficacy among the various products. Thus it appears possible that some of the whole-cell pertussis vaccines produced in various countries in the world and administered to infants and children might be less effective than others. The impact of these differences on the global burden of pertussis disease is unknown.

Another concern with whole-cell pertussis vaccines is the negative impact of high maternal antibody levels on infant immune responses. It has been demonstrated that the magnitude of the primary antibody response to whole-cell vaccine in infants depends on the preimmunization (transplacental) levels of antibody to PT, with higher circulating levels of maternally derived antibody being associated with significantly lower levels of postimmunization antibody.[248] In contrast, PT antibody responses to an acellular vaccine containing 12.5 μg each of PT and FHA were superior to those of the whole-cell vaccine and were not affected by prevaccination antibody levels.[248] Studies in developing countries have

17 not evaluated the impact of maternal antibody on immune responses to locally produced whole-cell vaccines in young children.

Controlled clinical trials of whole-cell vaccines It is well documented by controlled clinical trials that pertussis vaccine provides protection against clinical whooping cough after exposure in the majority of immunized people. The first convincing evidence was provided by studies in the Faroe Islands during two epidemics. [261] These studies showed that pertussis vaccine not only protected against disease but also ameliorated the severity of disease in immunized individuals who contracted the illness. Although studies with early vaccines produced inconsistent results,[11,185,279,282] clinical trials subsequent to standardization of the vaccines by the mouse protection test[278] demonstrated clear-cut, consistent efficacy.[278,283,284]

In more recent years, a number of field trials of acellular pertussis vaccines (see below under Efficacy Trials, 1992–1997) have incorporated whole-cell pertussis vaccines as controls and have provided some of the best data ever obtained about the efficacy of the conventional whole-cell vaccines. As mentioned previously, these studies suggest that whole-cell vaccines vary substantially in efficacy. (The following estimates reflect efficacy after three doses and, to the extent possible, consistent case definitions; however, none of these studies was fully blinded and randomized, and these estimates may be generous.) The Mainz[285] and Munich[286] studies produced efficacy estimates of 98% and 96%, respectively, for the German- produced Behringwerke vaccine; the U.S.-made Wyeth–Lederle whole-cell vaccine was reported to be 83% efficacious in the Erlangen trial;[228,287] and the Senegal trial reported the French-made Sanofi Pasteur whole-cell vaccine to be 96% efficacious.[288] In each of these trials, the whole-cell vaccine was more efficacious than the acellular product.

In marked contrast, the U.S.-made Connaught whole-cell vaccine had very low rates of efficacy after three doses: 48% in Sweden and 36% in Italy.[229,230] In the Swedish study, efficacy was nearly 74% for the first 6 months after the third dose of vaccine but declined rapidly after that time.[229] A British national survey of reported whooping cough from 1989 to 1990 determined that the efficacy of the Wellcome whole-cell vaccine, administered at 3, 5, and 10 months of age, was 87% and 93% during epidemic and nonepidemic periods, respectively.[289] Efficacy declined with age but remained high until the age of 8 years. A repeat survey was conducted in 1994 to determine whether efficacy had been altered by the change to an accelerated schedule of immunization at 2, 3, and 4 months of age (with no subsequent booster). Efficacy was not altered and was 94% overall for those subjects between 6 months and 5 years of age.[290] This accelerated schedule was also associated with a reduced rate of adverse reactions compared with the prior schedule.[291]

Other evidence of effectiveness of whole-cell vaccines Secular changes in morbidity and mortality There is no question that the widespread use of whole-cell pertussis vaccine in developed countries has been associated with a remarkable decline in reported pertussis. [185,211,212,292] However, it is also clear that mortality rates from pertussis were declining in at least

18 some of these countries even before the advent of the vaccine.[185,278,293,294] The latter reductions likely reflect a decrease in case-fatality rates as a result of such factors as improved social and economic conditions, better nutrition, and declines in concomitant infections that may have enhanced pertussis mortality.

Effects of the withdrawal of pertussis immunization Strong evidence of the benefits of pertussis vaccine was provided by unintended experiments that occurred in three developed countries when vaccine use was curtailed or abandoned. Japan initiated widespread immunization against pertussis in 1950, and over the ensuing years the numbers of reported cases and the numbers of deaths declined remarkably.[212,295] However, beginning in 1975, adverse events temporally associated with administration of whole-cell pertussis vaccine to young children led to a near-boycott of the vaccine and epidemic pertussis recurred. Hundreds of children died of pertussis during this period.[212] A similar experience occurred in England and Wales, in the context of negative publicity surrounding adverse events associated with vaccine. Rates of vaccine acceptance fell from approximately 75% to nearly 25% during the mid-1970s, major epidemics of pertussis ensued, and numerous children died.[211,296] In Sweden, the administration of pertussis vaccine was suspended in 1979 when pertussis outbreaks occurred despite high vaccination coverage, suggesting poor efficacy of the contemporary vaccine. The incidence of whooping cough then increased more than fourfold from 1980 to 1985, with several major outbreaks in subsequent years.[297,298] With the advent of routine pertussis immunization using acellular vaccines after completion of the vaccine efficacy trials in Sweden, pertussis rates have now declined markedly.[299] A review of the French experience with whole-cell pertussis vaccine over a period of 30 years showed persistent high efficacy of the product.[300]

Pertussis rates in vaccinated and unvaccinated communities Further evidence of the efficacy of whole-cell pertussis vaccine is provided by the observation that the reported incidence of pertussis disease varies inversely with vaccine acceptance rates. A study in England and Wales found that communities with low pertussis vaccine acceptance rates (<30%) had a 59% higher reported incidence of pertussis among children than did areas with high (>50%) acceptance rates; areas with intermediate acceptance rates had intermediate pertussis rates.[301] These findings were not explained by differences among the communities such as crowding and social class; indeed, after adjustment for these two social indicators, the inverse correlation with immunization status was, if anything, stronger. In the United States, where infant immunization for pertussis has been routine since the late 1940s or early 1950s, national surveillance demonstrated a greater than 95% reduction in pertussis; surveillance data from 1992 to 1994 found an overall whole-cell pertussis vaccine efficacy of 64% after three doses and of 82% after four or more doses.[231] Pertussis attack rates in immunized and unimmunized children during outbreaks Additional evidence for the efficacy of whole-cell pertussis vaccine is provided by community outbreaks of pertussis in which the attack rates of the disease in immunized children were compared with the rates in those who were incompletely or never immunized.[211,302] Although the methods of ascertainment and analysis vary, most studies indicate that the efficacy of

19 three or more doses of pertussis vaccine in protecting children against clinical disease during outbreaks is 80–90%, with incomplete immunization offering partial protection.[302] In children who contracted pertussis in spite of immunization, the disease was milder and complications were far less frequent, despite the fact that younger infants and children are more likely to have received inadequate or no immunization.[303,304] Studies conducted in Senegal also documented that breakthrough cases of pertussis among children vaccinated with whole-cell vaccine were of lesser severity and of reduced infectivity than in those seen in unimmunized children.[305,306]

Herd immunity after immunization In view of the fact that whole-cell pertussis vaccine is not 100% effective, it could be considered curious that morbidity and mortality from clinical pertussis have been negligible in countries with widespread immunization programs. This is a particularly interesting finding because surveillance statistics and studies demonstrating pertussis to be a common cause of protracted cough illness in adolescents and adults suggest that B. pertussis remains ubiquitous in these countries.[163,165,176,239–241] Attempts to model mathematically the decline in pertussis incidence attributable to widespread immunization with vaccines of 85% efficacy have underestimated the rates of decline of the disease.[307] Although other factors, such as social and economic changes, likely play a role, the most probable explanation is herd immunity, a complex phenomenon that varies among different infectious diseases and is difficult to measure with precision[308] (see Chapter 71). Herd immunity undoubtedly explains the cycles of outbreaks of pertussis every 3 or 4 years; after an outbreak, several years are required for the proportion of susceptible individuals to increase to a level that facilitates a new wave of rapid spread within a population. Finally, recent studies describing higher rates of pertussis disease in immunized children living in communities with large numbers of unimmunized children provide additional evidence for the role of herd immunity.[309]

Duration of immunity after whole-cell vaccines A number of studies have evaluated the duration of protection after immunization with whole- cell vaccine. Those that provide the longest period of evaluation indicate that protection declines by 50% over a period of 6–12 years.[310–312] These data are consistent with the incidence and serosurvey data cited previously that suggest an increase in rates of pertussis among 13– 17-year-olds, representing an interval of 7–12 years since last vaccination.[165] It is likely that the duration of protection is influenced by the vaccine used, the number of doses given, the vaccination schedule, and the level of circulatingB. pertussis capable of stimulating an amnestic response in previously immunized individuals.

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Adverse events with whole-cell vaccines

20 Overview Despite their clear benefits in reducing the substantial mortality and morbidity of pertussis, the whole-cell vaccines have long been recognized as one of our most reactogenic vaccines. They commonly cause reactions that are minor but burdensome, occasionally cause reactions that are transient but frightening, and uncommonly cause more serious, generally self-limited, adverse effects. For some time, there was substantial suspicion that whole-cell vaccines might be causally related to devastating outcomes such as encephalopathy or sudden infant death syndrome (SIDS), but several careful epidemiologic studies have largely dispelled these concerns.[313–315] Untoward events after pertussis immunization began to be of increasing concern to the public and to physicians in the early 1970s, particularly in countries where widespread vaccination had eliminated most disease. Vaccine-associated adverse events loomed large in the eyes of young parents and physicians who had never witnessed the morbidity and mortality of whooping cough. Widespread publicity about the alleged dangers of pertussis vaccine, coupled with declining disease rates in some countries and doubts about vaccine efficacy in others, resulted in near-abandonment of pertussis vaccine in several countries. Consequently, pertussis disease recurred.[211,212,297] In the United States, strong school-entry immunization laws enabled vaccination rates to be maintained despite widespread publicity about these concerns. However, extensive litigation over alleged personal injuries caused by the vaccine cost millions of dollars and contributed to the cessation of pertussis vaccine production by several manufacturers. Establishing or disproving cause and effect, particularly for events of major consequence, proved difficult. Although the original allegations of causation were largely anecdotal and based on the fallacious assumption that subsequences and consequences were synonymous, they raised great concern and stimulated the search for an improved vaccine. The relationships between whole-cell pertussis vaccine and fatal or disabling events were difficult to evaluate because of the rarity of such events; because vaccine was administered to infants at an age when disorders such as encephalopathy, infantile spasms, neurologic conditions, and SIDS were most likely to occur; because these disorders can arise from other causes; and because an absolute negative can never be proved. Earlier estimates of the rates of adverse events were not optimal because of lack of consideration of background rates, ill-defined criteria, and uncertainty of denominators. However, in the 1980s, more rigorous epidemiologic or interventional studies greatly improved the understanding of the incidence and spectrum of adverse events after whole-cell pertussis vaccine. Many of these studies, particularly those related to serious untoward events, were evaluated by a special committee of the Institute of Medicine (IOM) of the U.S. National Academy of Sciences.[313–315]Although these evaluations were reassuring to healthcare providers and parents alike, it was the development of less reactogenic acellular pertussis vaccines and their replacement of the whole-cell products that put an end to the long debate in developed countries over adverse events associated with whole-cell vaccines. Whole-cell pertussis vaccines remain widely used in developing countries, where concerns regarding adverse events do not seem to be important local issues. In light of the continuing move toward acellular vaccines, we restrict the discussion of adverse events associated with whole-cell vaccines to a summary of the key studies and conclusions.

21 Readers interested in a more thorough review of these data are referred to the second edition of this text.[316]

Nonfatal, nondisabling reactions Common reactions Minor local reactions, consisting of redness, swelling and pain at the site of injection, occur in about half of DTP recipients. Reactions occur five times more frequently after DTP than DT.[317– 319] Similarly, minor systemic reactions such as fever, irritability, and drowsiness are significantly more common after DTP than DT.[317–319] About half of the children who receive whole-cell pertussis vaccine experience some minor fever, with less than 1% having an elevation in temperature to 40.5°C (105°F).[317–320] Participants in the Multicenter Acellular Pertussis Trial (MAPT; see below) experienced somnolence at rates of 62% for whole-cell recipients and 43% for acellular vaccine recipients, [320] suggesting that the somnolence was, at least in part, an effect of the DTP vaccine. Some children were reported to have an unusual high-pitched cry. Somewhat more remarkable was a period of excessive crying, which may last several hours or longer after an injection. This incessant, inconsolable crying usually begins within 12 hours. Persistent crying of 1 hour or more occurred in both the DTP and DT groups in the Cody et al. study but was at least four times more common after DTP. Among those with persistent crying, the cry was described as high-pitched or unusual in 3.5% of the children.[318–320] These common reactions vary somewhat in frequency and severity among lots[321] and manufacturers. The vaccine schedule followed also may affect the incidence and severity of adverse reactions. In 1990, the schedule for DTP vaccination in the United Kingdom was changed from 3, 5, and 10 months of age to 2, 3, and 4 months of age. The new schedule was associated with a substantial reduction in postvaccination fever and redness of the injection site.[291] With the accelerated vaccination schedule in the United Kingdom, reaction rates for the whole-cell vaccine did not differ significantly from those of several acellular vaccines.[291] Reaction rates also vary with the number of prior DTP injections. In the Cody et al. study, local reactions increased in frequency with successive doses, including the preschool booster. [318,319,321] The incidence of fever also increased with successive doses through the 18-month booster, but was lower with the preschool booster. Conversely, persistent, inconsolable crying occurred most frequently with the initial dose and less often thereafter. In the MAPT, the incidence and severity of fever increased substantially with successive primary doses of the reference whole-cell vaccine.[320,322] Redness increased modestly; the frequency of pain, fussiness, anorexia, vomiting, and the use of antipyretics did not materially increase or decrease with successive doses; and drowsiness decreased.[320] In general, children who have experienced local or systemic reactions after pertussis vaccine have an enhanced likelihood of experiencing the same reaction with a subsequent dose.[323]

Uncommon reactions DTP is associated with febrile seizures (0.06% in the Cody et al. trial), and seizures occur at increased rates after DTP in children with personal or family histories of convulsions.[319,323– 330] However, simple convulsions, although distressing, are considered to be benign.[331] There is

22 no evidence to support the concern that seizures after the receipt of DTP might induce epilepsy.[332] Another worrisome but uncommon reaction to DTP is that of a strange shock-like state, termed a hypotonic-hyporesponsive episode (HHE), that usually has its onset within 12 hours of inoculation and may last for several hours but always resolves.[333] Neither death nor adverse sequelae have been observed after these episodes. The Cody et al. study detected an incidence of HHE of 0.06%.[319,321] The mechanism of this phenomenon is unknown. HHE has been seen with other vaccines, including acellular pertussis products, as described later.

Serious reactions allegedly caused by whole-cell pertussis vaccine Encephalopathy The most serious reaction that has been attributed to whole-cell pertussis vaccine is acute encephalopathy. The National Childhood Encephalopathy Study, conducted in Great Britain from 1976 to 1979, examined whether the frequency of DTP vaccination in children with encephalopathy was greater than expected. Based on 11 subjects who appeared to have residua 18 months after vaccination, it was estimated that acute encephalopathy with permanent brain damage occurred at the widely quoted rate of 1 per 310,000 doses, with a 95% CI of 1 in 54,000–5,310,000 doses. However, subsequent investigations cast doubt on most of these 11 diagnoses.[334–336] At 10-year follow-up the rates of death or other sequelae in these subjects were similar regardless of whether or not the onset of acute neurologic illness was temporally associated with DTP vaccination.[337] The results of the National Childhood Encephalopathy Study have been subjected to extensive analysis, reanalysis, challenge, and debate.[336–342]None of this scrutiny has overturned the initial cautious interpretation that the data suggested but did not prove a causal relationship between pertussis vaccine and permanent neurologic damage. Several U.S. studies also failed to show a relation between vaccine and acute encephalopathy leading to brain damage.[326,330] In 1994, the IOM concluded that the ‘balance of evidence is consistent with a causal relation between DTP and chronic nervous system dysfunction in children whose serious acute neurologic illness occurred within 7 days of DTP vaccination.’[314] However, the IOM was not able to determine whether the pertussis vaccine increased the number of children with chronic neurologic illness or was simply a precipitating event in children who would have nonetheless developed chronic neurologic dysfunction as a result of underlying brain or metabolic abnormalities. Infantile spasms Infantile spasms, which occur in about 40 per 100,000 infants,[343] have been reported in temporal association with pertussis vaccination.[344] Because infantile spasms typically present between 2 and 8 months of age, it is obvious that an association is occasionally seen by chance alone. Four studies have demonstrated no foundation for concern that DTP causes infantile spasms.[209,335,345–347] Sudden infant death syndrome Because SIDS occurs most often in the first 6 months of life,[348] it is to be expected by chance alone that some instances would be observed within a day or two of receipt of DTP. Several early reports suggested clustering of SIDS cases within a few days after the administration of DTP,[349–353] but subsequent studies found no evidence of a causal relationship between SIDS and

23 receipt of DTP.[12,354–361] The IOM panel, after a careful review of all studies, also concluded that no causal relationship existed.[313,362] Other serious conditions The IOM panel examined the evidence concerning an association between DTP and a variety of syndromes; their conclusions are summarized in Table 21-7.[313,362]

Table 21-7 -- Institute of Medicine Conclusions Regarding Causation of Serious Adverse Events by DTP Event Conclusion Evidence indicates causation Anaphylaxis Prolonged or inconsolable crying Febrile seizures Evidence consistent with causation Acute encephalopathy Hypotonic-hyporesponsive episodes Evidence does not indicate causation Afebrile seizures Hypsarrhythmia Infantile spasms Reye syndrome Sudden infant death syndrome Insufficient evidence to draw a conclusion Aseptic meningitis Chronic neurological damage Epilepsy Erythema multiforme or other rashes Guillain–Barre syndrome Hemolytic anemia Juvenile diabetes Learning or attention disorders Peripheral mononeuropathy Thrombocytopenia No evidence available either way Autism

Data from Howson CP, Howe CJ, Fineberg HV, (eds). Adverse effects of pertussis and rubella vaccines: A report of the Committee to Review the Adverse Consequences of Pertussis and Rubella Vaccines. Washington, DC: National Academy Press, National Academy of Sciences, 1991; Howson CP, Fineberg HV. Adverse events following pertussis and rubella vaccines: summary of a report of the Institute of Medicine. JAMA 267:392–396, 1992 Howson CP, Fineberg HV. The ricochet of magic bullets: Summary of the Institute of Medicine report, Adverse effects of pertussis and rubella vaccines. Pediatrics 89:318–324, 1992.

U.S. National Childhood Vaccine Injury Act Increasing litigation over alleged vaccine injuries and withdrawal from the marketplace of vaccines by several DTP manufacturers prompted the U.S. Congress in 1986 to pass the National Childhood Vaccine Injury Act, which provides compensation for certain untoward

24 events that occur within specified time periods after vaccination. In 1995, program rules were revised in light of the report of the IOM committee.[313,362] The replacement of whole-cell with acellular pertussis vaccines has markedly reduced the rates of adverse reactions temporally associated with pertussis vaccine,[363]resulting in a corresponding decline in vaccine injury claims.[364]

Development of acellular vaccines

Due to the common occurrence of minor but burdensome local reactions and less common but more severe systemic reactions, coupled with public anxiety over allegations of devastating complications following immunization with whole-cell vaccine, new, less reactogenic pertussis vaccines were sought.

An improved understanding of the biology of B. pertussis and the isolation of individual components of the organism important in disease pathogenesis and induction of clinical immunity led to the production of new vaccines. Sato and colleagues in Japan designed the first purified component (acellular) pertussis vaccines. The initial vaccines consisted predominantly of FHA, along with smaller amounts of inactivated PT and, in some cases, fimbrial proteins and PRN, and were known as Takeda-type vaccines. They soon were followed by additional acellular vaccines containing equal quantities of PT and FHA (termed Biken-type vaccines). Criteria for the licensure of the acellular vaccines in Japan included low toxicity in the mouse, documentation of mouse potency, diminished systemic and local reactivity in children, and antibody production in children similar to or exceeding that of the whole-cell vaccine. Demonstration of clinical protection by field trials was not required in Japan, although household-contact studies and pertussis surveillance after implementation of the acellular vaccines gave clear evidence of effectiveness. Since 1981, acellular pertussis vaccines have been used exclusively in Japan and have been very effective.[265–270] Reported pertussis currently is at an all-time low in Japan.[270,271]The encouraging results in Japan stimulated other industrialized nations to evaluate the Japanese acellular vaccines and to develop other acellular vaccines. Nearly two dozen acellular pertussis vaccines were designed, many were evaluated in immunogenicity and reactogenicity trials, and the efficacy and safety of a number were evaluated in field trials. These vaccines varied from one another with respect to their source, number of components, quantity of each component, method of purification, method of toxin inactivation, incorporated adjuvants, and excipients (Tables 21-3 and 21-4).[272] Unfortunately, identifying the optimum formulation for an acellular vaccine has proven difficult, because no simple method exists to determine the protective capability of a pertussis vaccine. The results of the mouse intracerebral protection test correlate reasonably well with the clinical protection afforded by whole-cell vaccine, but the test does not predict the efficacy of acellular pertussis vaccines.[210] Guiso and colleagues have found that the results of intranasal challenge in a murine model correlated with efficacy of selected acellular pertussis vaccines,[273] suggesting the possible utility of such tests in preclinical evaluation of candidate vaccines. Because the intracerebral mouse protection test does not provide a valid measure of the protective capability of the acellular pertussis vaccines, the potency of individual lots of these vaccines produced for the U.S. marketplace is evaluated by measurement of the antibody response to

25 PT (plus FHA, PRN, and fimbrial proteins, as applicable) in immunized mice, using an ELISA. Although human immunologic correlates of protection have been avidly sought, these efforts have met with only partial success, as described later in this chapter. Acellular pertussis vaccines have entirely replaced whole-cell pertussis products in the United States, Canada, Australia, some Asian and many European markets (Table 21-5).

Table 21-3 -- Key Characteristics of Selected Acellular Pertussis Vaccines[*]

Micrograms of Pertussis Diphtheria Tetanus Antigen per Dose Toxoid[‡] Toxoid[‡] Manufacturer or Evaluated in Distributor Vaccine[†] MAPT PT FHA PRN FIM

SanofiPasteur (Canada) Tripacel; Yes 10 5 3 5 15 5 [§] DAPTACEL

SanofiPasteur (Canada) HCPDT No 20 20 3 5 15 5 [§]

SanofiPasteur (France) Triavax; Yes 25 25 — — 15 5 Triaxim

SanofiPasteur (USA) Tripedia Yes 23.4 23.4 — — 6.7 5

Baxter Laboratories Certiva No 40 — — — 15 6

Chiron Vaccines Acelluvax Yes 5 2.5 2.5 — 25 10

GlaxoSmithKline Infanrix Yes 25 25 8 — 25 10

Japan National NIH-6[|] No 23.4 23.4 — — — — Institutes of Health

Japan National JNIH-7 No 37.7 — — — — — Institutes of Health

SmithKline Beecham SKB-2 Yes 25 25 — — 25 10

26 Micrograms of Pertussis Diphtheria Tetanus Antigen per Dose Toxoid[‡] Toxoid[‡] Manufacturer or Evaluated in Distributor Vaccine[†] MAPT PT FHA PRN FIM

Biologicals

Wyeth ACEL-IMUNE Yes 3.5 35 2 0.8 9 5 Pharmaceuticals[¶]

FHA, filamentous hemagglutinin; FIM, fimbrial proteins; MAPT, Multicenter Acellular Pertussis Trial; PRN, pertactin; PT, pertus sis toxin.

Compositions may differ in various markets; local suppliers should be consulted as necessary. Some products are no longer available, but are included because knowledge of their composition is important to understanding the results of the efficacy trials.

† Trade names (most common trade names, if multiple names exist) except as follows: HCPDT is the ‘hybrid’ evaluated in the 1993

‡ Measured in Limit of Flocculation units per dose.

§ FIM component is a mixture of FIM-2 and FIM-3. In MAPT, PT was 10 μg; FHA, 5 μg.

| A Biken vaccine, similar to Tripedia.

¶ Contains approximately 40 μg (but not more than 60 μg) of pertussis antigen proteins, consisting of approximately 86% FHA, approximately 8% PT, approximately 4% PRN, and approximately 2% FIM-2.

Table 21-4 -- Additional Characteristics of Selected Acellular Pertussis Vaccines[*]

27 Manufacturer or Aluminum, Trace Distributor Vaccine[†] How Toxoided mg Diluent Preservative Constituents

SanofiPasteur Tripacel; Glutaraldehyde 0.33[|] PBS Phenoxyethanol Glutaraldehyde, (Canada) DAPTACEL PS

SanofiPasteur HCPDT Glutaraldehyde 0.33[|] PBS Phenoxyethanol Glutaraldehyde, (Canada) PS

SanofiPasteur Triavax; Glutaraldehyde 0.30[§] n/a Thimerosal n/a (France) Triaxim

SanofiPasteur (USA) Tripedia Formaldehyde 0.17[¶] PBS None Formaldehyde, gelatin, PS

[§] Baxter Laboratories Certiva H2O2 0.50 PBS Thimerosal none

Chiron Vaccines Acelluvax[‡] Genetic 1.0[§] n/a Thimerosal n/a

GlaxoSmithKline Infanrix Formaldehyde[#] 0.625[§][#] Saline Phenoxyethanol Formaldehyde, PS

Japan National JNIH-6 Formaldehyde 0.08 PBS Thimerosal Formaldehyde Institutes of Health

Japan National JNIH-7 Formaldehyde 0.075 PBS Thimerosal Formaldehyde Institutes of Health

SmithKline SKB-2 Formaldehyde 0.50[§] Saline Phenoxyethanol Formaldehyde, PS Beecham Biologicals

Wyeth ACEL-IMUNE Formaldehyde 0.23[**] PBS Thimerosal Formaldehyde, Pharmaceuticals gelatin, PS n/a, information not available; MAPT, Multicenter Acellular Pertussis Trial; PBS, phosphate-buffered saline; PS, polysorbate-80; TNM, tetranitromethane.

28 * Compositions may differ in various markets; local suppliers should be consulted as necessary. Aluminum content is per dose. Some products are no longer available, but are included because knowledge of their composition is important to understanding the results of the efficacy tr ials.

† Trade names (most common trade name, if multiple names exist) except as follows: HCPDT is the ‘hybrid’ Tripacel evaluated in the 1993 Stockholm trial (otherwise, used only in combinations); JNIH-6 and JNIH-7 were the acellular vaccines used in the 1986 Swedish trial; SKB-2 was an experimental 2- component DTaP evaluated in the 1992 Stockholm trial.

‡ Pertussis components are formaldehyde-stabilized. Aluminum content was 0.35 mg in MAPT.

§ As aluminum hydroxide.

| As aluminum phosphate.

¶ As aluminum potassium sulfate.

# PT component detoxified with both formaldehyde and glutaraldehyde. In MAPT, aluminum content was 0.50 mg.

** A mixture of aluminum hydroxide and aluminum phosphate.

Table 21-5 -- Pertussis Immunization Schedules Recommended by Selected National Authorities, as of September 2006[*]

Adolescent-Adult Country Primary Vaccination Schedule Pediatric Boosters Boosters

Global: Most countries in Africa, the Middle East, and Asia (except as shown otherwise herein)

EPI Programs 6, 10, 14 weeks: DTwP 18 mos to 4 yrs: DTwP

North America

29 Adolescent-Adult Country Primary Vaccination Schedule Pediatric Boosters Boosters

Canada 2, 4, 6 mos: DTaP-IPV-Hib 18 mos: DTaP-IPV-HIB; 4-6 yrs:14–16 yrs: Tdap (or Td) DTaP-IPV

United States 2, 4, 6 mos: DTaP or DTaP-IPV-HB15-18 mos: DTaP or DTaP-Hib; 11 yrs: Tdap 4-6 yrs: DTaP

Mexico 2, 4, 6 mos: DTwP-Hib-HB 2 and 4 yrs: DTwP

Europe

Austria 3, 5, 7 mos: DTaP-IPV-Hib-HB 16 mos: DTaP-IPV-Hib-HB; 7 13–16 yrs and yrs: Td-IPV decennially: TdaP

Belgium 2, 3, 4 mos: DTaP-Hib-IPV-HB 13–18 mos: DTaP-Hib-IPV-HB 14–16 yrs: Tdap (catch- up)

Czech Republic 9 weeks, 3 and 4 mos: DTwP/Hib 18–20 mos and 5 yrs: DTwP

Denmark 3, 5, 12 mos: DTaP-IPV-Hib 5 yrs: TdaP-IPV

Finland 3, 5, 12 mos: DTaP-HB-IPV 6 yrs: DTaP-IPV 14–15 yrs: TdaP

France 2, 3, 4 mos: DTaP-IPV-Hib or 16–18 mos: DTaP-IPV-Hib or 11–13 yrs: DTaP-IPV DTaP-IPV-Hib-HB DTaP-IPV-Hib-HB

Germany 2, 3, 4 mos: DTaP-IPV-Hib-HB 11–14 mos: DTaP-IPV-Hib-HB; 9–17 yrs: Tdap 5-6 yrs: Tdap

Greece 2, 4, 6 mos: DTaP-IVP-Hib-HB 18 mos and 4-6 yrs: DTaP

Hungary 3, 4, 5 mos: DTwP 3 yrs and 6 yrs: DTwP

30 Adolescent-Adult Country Primary Vaccination Schedule Pediatric Boosters Boosters

Iceland 3, 5, 12 mos: DTaP-IPV-Hib 4–5 yrs: DTaP-IPV

Ireland 2, 4, 6 mos: DTaP-IPV-Hib 4–5 yrs: DTaP-IPV

Israel 2, 4, 6 mos: DTaP-IPV-Hib 12 mos: DTaP-IPV-Hib; 7 yrs: DTaP-IPV

Italy 3, 5, 11–12 mos: DTaP-IPV-Hib- 5–6 yrs: DTaP 11–12 yrs or 14–15 yrs: HB Tdap

Luxembourg 2, 3 mos: DTaP-IPV-Hib-HB; 4 11–12 mos: DTaP-IPV-Hib-HB; 12–15 yrs: TdaP mos: DTaP-IPV-Hib 5 yrs: Tdap

The Netherlands 2, 3, 4 mos: DTaP-IPV-Hib 11 mos: DTaP-IPV-Hib; 4 yrs: DTaP-IPV

Norway 3, 5, 11–12 mos: DTaP-IPV-Hib 6–8 yrs: DTaP-IPV

Poland 2, 3–4, 5 mos: DTwP 16–18 mos: DTwP; 6 yrs: DTaP

Portugal 2, 4, 6 mos: DTaP-IPV-Hib-HB 18 mos: DTaP-Hib; 5–6 yrs: DTaP-IPV

Russia 3, 4.5, 6 mos: DTaP or DTaP-IPV 18 mos: DTaP or DTaP-IPV

Slovakia 2, 4, 10 mos: DTwP-IPV-Hib 24 mos: DTwP; 5 yrs: DTwP

Spain 2, 4, 6 mos: DTaP-IPV-Hib-HB 15–18 mos: DTaP-IPV-Hib [13 yrs] + every 10 yrs: Tdap

Sweden 3, 5, 12 mos: DTaP-IPV-Hib 10 yrs: Tdap

31 Adolescent-Adult Country Primary Vaccination Schedule Pediatric Boosters Boosters

Switzerland 2, 4, 6 mos: DTaP-IPV-Hib-HB 15–24 mos: DTaP-IPV-Hib-HB; 11–15 yrs: Tdap 4–7 yrs:

DTaP-IPV

United Kingdom 2, 3, 4 mos: DTaP-IPV-Hib 3–5 yrs: DTaP-IPV

Central and South America (most countries not shown follow a schedule similar to one of the following)

Argentina 2, 4, 6 mos: DTwP-Hib 18 mos: DTwP-Hib; 6 yrs: DTwP

Brazil 2, 4, 6 mos: DTwP-Hib 15 mos and 4-6 yrs: DTwP

Chile 2, 4, 6 mos: DTwP 18 mos and 4 yrs: DTwP

El Salvador 2, 3, 6 mos: DTwP-Hib-HB 15 mos and 4 yrs: DTwP

Nicaragua 2, 4, 6 mos: DTwP-Hib-HB 18 mos: DTwP

Peru 2, 4 mos: DTwP-Hib-HB; 3 mos, DTwP

Trinidad/Tobago 3, 4, 6 mos: DTwP-Hib-HB 18 mos and 5 yrs: DTwP

Uruguay 2, 4, 6 mos: DTwP-Hib-HB 12 mos: DTwP-Hib-HB; 5 yrs: DTwP

Asia (most countries not shown generally follow the EPI schedule)

Australia 2, 4, 6 mos: DTaP-IPV-HB or 4 yrs: DTaP-IPV 15–17 yrs: Tdap

32 Adolescent-Adult Country Primary Vaccination Schedule Pediatric Boosters Boosters

DTaP-IPV-Hib-HB

China 3, 4, 5 mos: DTwP 18–24 mos: DTwP

Indonesia 2, 3, 4 mos : DTwP or DTwP-HB

Japan 3–12 mos: 3 doses DTaP 15 mos: DTaP

Korea 2, 4, 6 mos: DTaP 15–18 mos and 4–6 yrs: DTaP

Republic of 2, 3, 5 mos: DTwP-Hib 18 mos: DTwP

Malaysia

New Zealand 6 wks, 3 mos, 5 mos: DTaP-IPV 15 mos: DTaP-Hib; 4 yrs: 11 yrs: Tdap-IPV DTaP-IPV

Taiwan 2, 4, 6 mos: DTaP 18 mos: DTaP

Thailand 2, 4, 6 mos: DTwP or DTwP-HB 18–24 mos and 4–5 yrs: DTwP

As of September 2006, WHO maintained an interactive resource that displayed recent (but not necessarily current) immunization schedules by selected country at http://www.who.int/immunization_monitoring/en/globalsummary/scheduleselect.cfm . The same information, plus demographic data and the incidence of vaccine-preventable diseases, was available at http://www-nt.who.int/vaccines/globalsummary/Immunization/CountryProfileSelect.cfm .

* Compiled from multiple sources. In many countries, products based on whole-cell pertussis vaccine are used in the national or public programs (shown in the above table), whereas products based on acellular vaccines often are used in private practice. In such countries, recommended schedules for private practice typically are based on US or Western European schedules.

33 Results of vaccination: acellular pertussis vaccines

Immune responses to acellular vaccines

Humoral immunity

Numerous immunogenicity and reactogenicity studies have been published, each evaluating one of the various acellular pertussis vaccines. Making comparisons across such studies, however, is an uncertain process, given the variations in study design, study populations and serologic assays. To provide such comparisons and facilitate selection of candidate vaccines for anticipated efficacy trials, the National Institute of Allergy and Infectious Diseases (NIAID) sponsored the MAPT in six of its Vaccine Treatment and Evaluation Units from 1991 to 1992. Thirteen acellular and two whole-cell vaccines were evaluated in the MAPT, including all but one of the acellular vaccines subsequently evaluated in efficacy trials. Although this last vaccine was not made available for the MAPT, it was evaluated thereafter at one of the Vaccine Treatment and Evaluation Units using the MAPT protocol, procedures, and data forms; sera were evaluated in one of the MAPT reference laboratories. Immunogenicity and reactogenicity results from that study are presented here, along with the MAPT results, to provide the most complete available comparison of these vaccines.

Healthy infants enrolled in the MAPT were randomized to receive one of the study vaccines (see Table 21-8) at 2, 4, and 6 months of age. Whole-cell vaccines made by Lederle Laboratories (the reference or control vaccine) and the Massachusetts Public Health Biologic Laboratories also were evaluated. Sera were obtained before the first immunization and 1 month after the third immunization. Serologic assays included ELISA antibody to PT, FHA, PRN, and fimbrial proteins; Chinese hamster ovary cell toxin neutralization and agglutination assays; and assays of diphtheria and tetanus antitoxin.[272]

Table 21-8 -- Antibody Levels One Month Following the Third Dose of Vaccine: Results from the Multicenter Acellular Pertussis Trial and a Followup Trial[*]

Geometric Mean Antibody Level (95% CI) Following Immunization at 2, 4, and 6 Months

Manufacturer or Distributor Vaccine[†] PT FHA PRN FIM

SanofiPasteur (Canada) Tripacel 36 (32–41) 37 (32–42) 114 (93–139) 240 (204–282)

SanofiPasteur (Canada) CLL-3F2 38 (33–44) 36 (31–41) 3.4 (3.1–3.6) 230 (183–290)

SanofiPasteur (France) Triavax 68 (60–76) 143 (126–161) 3.3 (3.1–3.6) 1.9 (1.6–2.1)

SanofiPasteur (USA) Tripedia 127 (111–144) 84 (73–95) 3.5 (3.2–3.9) 2.0 (1.7–2.3)

Baxter Laboratories Certiva 54 (41–71) 1.1 (1.0–1.2) n/a n/a

34 Geometric Mean Antibody Level (95% CI) Following Immunization at 2, 4, and 6 Months

Biocine Sclavo BSc-1 180 (163–200) 1.2 (1.1–1.4) 3.4 (3.1–3.7) 1.8 (1.7–2.0)

Chiron Vaccines Acelluvax 99 (87–113) 21 (18–25) 65 (53–79) 1.9 (1.7–2.1)

GlaxoSmithKline Infanrix 54 (46–64) 103 (88–120) 185 (148–231) 1.9 (1.7–2.2)

Massachusetts Public Health SSVI-1 99 (87–111) 1.2 (1.1–1.3) 3.4 (3.1–3.6) 2.1 (1.8–2.4) Biologic Labs

Michigan Department of Public Mich-2 66 (59–75) 237 (213–265) 3.2 (3.0–3.4) 2.0 (1.8–2.3) Health

SmithKline Beecham BiologicalsSKB-2 104 (94–116) 110 (99–122) 3.3 (3.1–3.5) 1.9 (1.7–2.1)

Speywood (Porton) Por-3F2 29 (25–33) 20 (17–23) 3.0 (3.0–3.1) 361 (303–430) Pharmaceuticals

Wyeth Lederle Vaccines and LPB-3P 39 (32–48) 144 (127–163) 128 (109–150) 19 (13–27) Pediatrics

Wyeth Pharmaceuticals ACEL- 14 (12–17) 49 (45–54) 54 (47–62) 51 (41–63) IMUNE

Wyeth Lederle Vaccines and Whole-cell 67 (54–83) 3.0 (2.7–3.4) 63 (54–74) 191 (161–227) Pediatrics

CI, confidence interval; FHA, filamentous hemagglutinin; FIM, fimbrial proteins; MAPT, Multicenter Acellular Pertussis Trial; n/a, not available; PRN, pertactin; PT, pertussis toxin.

* Results for Certiva are from a separate study conducted at an MAPT study center after completion of the MAPT, using the MAPT protocol, procedures, and data forms; sera were assayed at one of the MAPT reference laboratories.

† For those vaccines without known trade names, designation reflects source and composition of vaccine. [209] For branded products, note that the licensed formulation may differ from that of the vaccine evaluated in MAPT. Adapted with permission from Edwards KM, Meade BD, Decker MD, et al. Comparison of 13 acellular pertussis vaccines: Overview and serologic response. Pediatrics 96: 548– 557, 1995.

Each vaccine produced significant increases in antibodies directed against its included antigens, which most often equaled or exceeded those produced by the reference whole-cell vaccine (Table 21-8).

35 [272] Nonetheless, postimmunization antibody levels differed substantially among the acellular vaccines. For PRN and fimbrial proteins, and to some extent for FHA, antibody levels tended to correlate with the quantity of antigen included in the vaccine. For PT, postimmunization antibody levels did not correlate well with the quantity of antigen in the vaccine, suggesting that manufacturing techniques were important in determining the immunogenicity of the particular PT component of each vaccine. No acellular vaccine was most or least immunogenic with respect to all included antigens.

Cell-mediated immunity

Animal studies,[365–368] persistent pertussis infection in human immunodeficiency virus-infected patients, [369,370] and clinical trials demonstrating protection against pertussis in the face of persistence of cell- mediated immunity (CMI), and waning antibody levels have suggested an important role for CMI in the host defense against pertussis. Mills and colleagues showed that the rate of B. pertussis clearance following respiratory challenge of immunized mice correlated with vaccine efficacy in children.[371] Using mice with targeted disruptions of the interferon-γ (IFN-γ) receptor, interleukin-4, or immunoglobulin heavy-chain genes, they demonstrated an absolute requirement for antibody in bacterial clearance and a critical role for IFN-γ in immunity generated by previous infection or immunization with the whole-cell pertussis vaccine.[371] Passive immunization experiments suggested that protection early after immunization with aPvaccines was mediated by antibody against multiple protective antigens. In contrast, more complete protection conferred by previous infection or immunization with the wP vaccines reflected the induction of Th1 cells. These findings suggested that the mechanism of immunity against B. pertussis involved both humoral and cellular immune responses directed against several protective antigens.

As part of the comprehensive evaluation of aP vaccines in adults and children, investigators characterized pertussis-specific CMI after the administration of aP vaccine. Initial studies in adults[372– 376,376a] and subsequent studies in infants[377,377a] and toddlers[378–380]demonstrated that aP vaccine induced specific T-cell responses to the antigens included in the vaccine, which increased progressively with time after vaccination.[381] Interleukin-2 and IFN-γ were induced preferentially, and Th1 cells were involved in the immune responses.[83] It was also learned that CMI responses persisted with time, while antibody levels waned, as shown in Table 21-9. A small cohort of children had CMI responses evaluated on multiple occasions during the Italian acellular pertussis vaccine efficacy trial. A marked decline in anti-PT IgG levels was noted over time and was inversely correlated with substantial increases in the proportion and magnitude of CMI responses to the same antigen more than 42 months after vaccination.[378,380,381] Further support for the role of CMI in disease prevention was provided by an investigation of a pertussis outbreak in a Finnish school; students with persistent CMI responses were protected from disease, whereas no correlation was found between protection and antibody levels.[382]

Table 21-9 -- Antibody and Cell-mediated Immune (CMI) Responses to Pertussis Toxin in a Cohort of Children ≤48 Months Old Who Were Followed Longitudinally After Acellular Vaccine

36 Immunoglobulin Responses CMI Proliferative Responses

Age, Months After CMI months Vaccine Seroresponders/Total GMT (95%CI) Responders/Total Mean SI

2 1/19 1.3 (0.9–1.8) 0/19 1.2 (0.3–3)

7 1 19/19 103 (103– 4/19 2.7 (0.3– 104) 12.8)

20 14 8/19 6.4 (5.7–7.1) 8/19 6.7 (0.5– 26.3)

48 42 1/19 2.0 (1.5–2.6) 17/19 31.5 (1–203)

Adapted from Zepp F, Knuf M, Habermehl P, et al. Pertussis-specific cell-mediated immunity in infants after vaccination with a tricomponent acellular pertussis vaccine. Infect Immun 64:4078–4084, 1996.

Seroresponse is defined as a serum antibody titer > 4 times the minimal detection limit. Stimulation index (SI) is the ratio of counts per minute for stimulated vs unstimulated lymphocytes. A CMI response is defined as an SI >4.

In a recently published study, both pertussis-specific cell-mediated immunity (CMI) and humoral immunity were evaluated in adolescents 3 years after they received an acellular pertussis booster immunization. Pertussis-specific CMI levels persisted at greater than prebooster levels throughout the follow-up period. Antibody titers declined over time but remained significantly higher than prebooster levels.[383] Studies of CMI in recipients of acellular pertussis vaccines, in those infected with wild-type B. pertussis, and in individuals suffering adverse reactions to acellular vaccines should continue.

Immune correlates of protection

The establishment of an immune correlate of protection is important for all vaccines, but is particularly needed for acellular pertussis vaccines given that the old ‘gold standard,’ the mouse protection test, does not appear to predict aP vaccine potency adequately. Immune correlates of protection typically are established in randomized, placebo-controlled efficacy trials in which the attainment of a particular postvaccination level of immunity is correlated with prevention of disease. Early studies from the United Kingdom had suggested that measurable agglutinin titers in serum after whole-cell vaccination correlated with protection against pertussis disease.[264,384] One of the stated goals of the 1986–1987 Swedish efficacy trial evaluating the one- or two-component Japanese-made acellular vaccines was to establish serologic correlates of protection. However, much to everyone's dismay, postvaccination antibody levels of PT and FHA did not correlate with clinical protection. A number of possible explanations were proposed for this disappointing result:[385] Postimmunization antibody levels may have poorly predicted antibody levels at the time of exposure, reflecting the lack of data on the kinetics of antibody decline after immunization; antibody assays may have measured the wrong

37 epitopes; or perhaps protection was conferred not by humoral antibody but instead by CMI or mucosal immunity.

In several of the acellular pertussis vaccine efficacy trials conducted in Europe in the mid-1990s, efforts were made to determine immune correlates of protection. A nested household study was conducted as part of the 1992 Stockholm efficacy trial, which included a DT (placebo) arm, a U.S. whole- cell DTP vaccine, a two-component acellular vaccine and a five-component acellular vaccine. Serum samples obtained at 1 and 2.5 years of age and within 4 months prior to exposure, or acute serum samples obtained at least 6 months after the third dose, were used as pre-exposure serum samples for 209 household-exposed children.[83] The results of this study indicated that vaccine efficacy against typical pertussis after household exposure to B. pertussis was 75% for the five-component acellular vaccine, 42% for the two-component vaccine, and 29% for the licensed U.S. whole-cell vaccine when compared to the DT placebo (it is expected that efficacy estimates from a household contact study will differ from those obtained in a prospective randomized trial, given the highly variable nature and intensity of household exposure). Logistic regression analyses demonstrated statistically significant correlations between clinical protection and the presence in pre-exposure sera of IgG antibodies against pertactin, FIM-2/3, and pertussis toxin. Subjects with PT antibody levels exceeding the authors’ analytic threshold of 5 units/mL, but with FIM and PRN antibodies below that threshold, had a computed vaccine efficacy of 46%; those with PT and FIM levels both above the threshold had an efficacy of 72%; those with PT and PRN levels above the threshold, 75%; and those with all three antibody levels above the threshold, 85%. The authors concluded that multicomponent pertussis vaccines of proven high efficacy used in the Swedish efficacy trials induced higher antibody levels against PRN and FIM-2/3 than did the less efficacious vaccines evaluated in the same trials, and that anti-PRN, anti-FIM-2/3, and anti-PT may be used as surrogate markers of protection against pertussis for multicomponent acellular and whole-cell vaccines.

A different U.S.-licensed DTP vaccine, a four-component acellular vaccine, and an open-label control group were compared in a randomized, controlled trial conducted in Erlangen, Germany.[228,386] Sera were collected from vaccinees after the third and fourth doses of vaccine and at comparable time periods in DT vaccine recipients. In addition, sera were collected from a random sample of subjects in each vaccine group at approximately 3-month intervals to construct antibody kinetics curves. This allowed estimation of the specific levels of antibody to PT, FHA, PRN, and FIM-2 at the time of exposure in the household setting. The imputed geometric mean antibody titers to PT, PRN, and FIM-2 at the time of household exposure to pertussis infection were higher (P<0.07 or lower) in noncases compared with cases. A multivariate classification tree analysis found that only PRN and PT were significantly associated with protection. Subjects with an imputed PRN value of 7EU/mL or less had a 67% chance of infection, regardless of the PT value. No subjects with a PRN value of 7EU/mL or greater and a PT value of 66EU/mL or greater were cases, but, if the PRN value was 7EU/mL or greater and the PT value was 66EU/mL or less, the predicted probability of being a case was 31%. Logistic regression analysis also found that high versus low PRN values were associated with prevention of illness following household exposure. In the presence of antibody to PRN, PT, and FIM-2, the additional presence of antibody to FHA did not contribute to protection.

38 The similarities in the findings in these two studies are noteworthy, but it must be remembered that no efficacious one- or two-component acellular pertussis vaccines were evaluated in these studies; the results may inform us well as to the correlates of protection for the specific vaccines evaluated, while failing to elucidate correlates that are generalizable to all acellular pertussis vaccines. As Hewlett and Halperin stated in their editorial accompanying the publication of these data, ‘Over interpretation of these data is a significant risk and must be assiduously avoided.’ They cautioned that a vaccine containing PT alone was shown to be efficacious in the Göteborg trial and that the presence of PRN and fimbrial proteins therefore is not essential to protection afforded by acellular vaccines.[387]

Controlled clinical trials of acellular vaccines

Results are available from nine large efficacy trials of acellular pertussis vaccine that were initiated between 1985 and 1993 in Europe or Africa. The efficacy trials differed by many char-acteristics: type of study, study population, prevalence of pertussis and other diseases in the community, number of immunizations, timing of immunizations, choice of comparison or control vaccines, methods of surveillance, case definitions, and details of the laboratory support used to evaluate fulfillment of the case definition. These differences confound interpretation of the trials and prevent a simple, direct comparison of their primary efficacy results.

In evaluating these efficacy trials, there are several independent goals: to position correctly the evaluated vaccine within the spectrum of available vaccines, to draw inferences concerning the influence on efficacy of various vaccine characteristics, and to draw inferences concerning the effect on vaccine evaluation of various study design characteristics. Various deviations from the ideal study design are likely to affect these goals differentially; that is, a study that poses difficulties in accomplishing one goal may nonetheless be useful for accomplishing other goals.

The objectives of pertussis vaccination also play a role in evaluating measurements of efficacy. If the societal goal is focused on the prevention of severe disease, then a study's inability to detect mild illness (or determine efficacy against that endpoint) may not be important. However, if the goal is to prevent pertussis infection, then mild illnesses must be detected, even though such illnesses may be more difficult to ascertain than classical whooping cough. To the extent that vaccines modify but do not prevent illness, the case definition chosen could have a major impact on interpretation of the efficacy, and hence the benefits, of the vaccine.

Although frustration with the limitations of these trials has led to calls for ‘definitive studies’ that would resolve remaining questions[388,389] it is doubtful that any sponsor, public or private, would find the enormous expense of such a study to be both in their interest and of sufficient priority to compete successfully for funds. Thus these trials will likely remain our only sources of efficacy data, and we must make use of them as best we can.

39 1986 Swedish efficacy trial

The first large-scale efficacy trial of acellular vaccine was conducted in 1986 in Stockholm, Sweden, where routine pertussis immunization had been discontinued in 1979 and pertussis had become endemic.[297] The randomized, double-blind, placebo-controlled trial (Table 21-10) evaluated a Biken vaccine containing 23.4 μg each of PT and FHA (denoted JNIH-6; see Tables 21-3 and 21-4),[389,390] a monocomponent Japanese National Institues of Health vaccine prepared for the purposes of this study and containing 37.7 μg of PT (denoted JNIH-7),[389,390] and vaccine diluent given as a placebo.[135] There was no whole-cell control group. A two-dose schedule was used; infants were enrolled and immunized at 5–11 months of age, with the second dose given 8–12 weeks later.

Table 21-10 -- Overview of Nine Acellular Pertussis Vaccine Efficacy Trials

Ages of Study Groups and Vaccines Vaccinatio Comments on Study Evaluated n Surveillance Design Location, Year Acellular[* Placeb Duration[† Begun ] Whole-Cell o ] Active Passive

Randomized, fully blinded, controlled comparative studies

StockholmJNIH-6 None Diluent 5–11 mos, 15 mos[‡] Telephon Parents Lack of whole-cell , 1986[328] then 8–12 e q. instructe control hampered wks later month d to interpretation. report Schedule (2 doses, relatively late in infancy) makes comparisons to other trials difficult. Later analyses revealed differential sensitivity of culture and of serology in vaccine vs placebo groups

JNIH-7

StockholmSKB-2 DT 2, 4, 6 mos23.3 mos Telephon Parents Stockholm 1992 and , 1992[181] ∠ e q. 6–8 instructe Italy are the Connaught wks d to benchmark studies: report prospective, fully randomized and

40 Ages of Study Groups and Vaccines Vaccinatio Comments on Study Evaluated n Surveillance Design Location, Year Acellular[* Placeb Duration[† Begun ] Whole-Cell o ] Active Passive

blinded, with both whole-cell and placebo (DT) control groups. Each study evaluated 2 candidate acellular vaccines head-to-head, using the same immunization schedules and nearly identical case definitions and diagnostic procedures

Tripacel[§] 23.8 mos

Italy, Infanrix Connaught[|] DT 2, 4, 6 mos17 mos Telephon Parents 1992[182] e q. instructe month d to report

Acelluvax

StockholmSKB-2 Wellcome None 88% at 3, 7.2 mos Clinic Daily No placebo control , 1993[329] 5, 12 mos; visits at 5,check of group, thus no 12% at 2, 12, 18 culture absolute efficacy 4, 6 mos mos reports estimates, hampering comparisons to other studies. Formulation of Connaught Canada 5-component vaccine changed since Stockholm 1992, further hampering comparisons; however, Acelluvax ar m presumably

41 Ages of Study Groups and Vaccines Vaccinatio Comments on Study Evaluated n Surveillance Design Location, Year Acellular[* Placeb Duration[† Begun ] Whole-Cell o ] Active Passive

comparable to Italy

Acelluvax 21.5 mos

HCPDTl[§] 21.5 mos

Randomized, fully blinded, controlled studies

Göteborg Certiva None DT 3, 5, 12 17.5 mos Telephon Parents Vaccination schedule (Sweden), mos e q. instructe and lack of whole-cell 1991[330] month d to control group hamper report comparisons to other studies

Other studies

Senegal, Triavax Pasteur DT 2, 4, 6 mos21 mos Field None Prospective, double- 1990[229] Merieux worker blind, randomized for visit q. relative risk of DTaP week vs DTP. Absolute efficacy based on case-contact study using nonrandomized DT/no vaccine group that was unblinded to parents and, probably, to field workers performing initial case detection. Investigating physicians said to be blinded

Erlangen ACEL- DT 3, 5, 7, 17 25.6 mos Telephon Parents Prospective, double- (Germany)IMUNE ∠ mos e q. 2 instructe blind, randomized for Lederle , 1991[180] weeks d to relative risk of DTaP report to vs DTP. Absolute PMD efficacy based on

42 Ages of Study Groups and Vaccines Vaccinatio Comments on Study Evaluated n Surveillance Design Location, Year Acellular[* Placeb Duration[† Begun ] Whole-Cell o ] Active Passive

comparison to a nonrandomized DT group that was unblinded to parents and, occasionally, to investigators

Mainz Infanrix Behringwerk DT 3, 4, 5 mos23 mos None Physician Household contact (Germany) e or report of study. Vaccine , 1992[226] SmithKline contact assignment not Beecham by parentrandomized; parents and physicians responsible for initial case detection not blinded. Central case investigators were said to be blinded

Munich, Tripedia Behringwerk DT 3, 5, 7 mosn/a None Physician Nonrandomized 1993[227,331] e report of (vaccine chosen by contact parents), unblinded by parent(parents and investigators knew vaccine status) case- control study

DT, diphtheria and tetanus toxoids vaccine; DTaP, DT plus acellular pertussis vaccine; DTP, DT plus whole-cell pertussis vaccine; HCPDT, hybrid component pertussis-diphtheria-tetanus vaccine; n/a, not available or not applicable; PMD, private physician; q., quaque (each, every).

* Descriptive name given for those without trade name. See Tables 21-3 and 21-4 for further details.

† Mean duration of surveillance. Subjects were eligible for inclusion as cases from time of last dose (Stockholm 1992, Stockholm 1993), from 28–30 days after last dose (Stockholm 1986, Italy, Göteborg, Senegal, Mainz), or from 14 days after last dose (Erlangen) of DTaP.

43 ‡ Passive unblinded surveillance, augmented with inquiries mailed to parents every 6 months and follow- up of positive cultures reported to the National Bacteriology Laboratory, continued for an additional 3 years.

§ Tripacel and HCPDT are similar, except that Tripacel contains 10 μg PT and 5 μg FHA, as compared to 20 μg of each in HCPDT.

| U.S.-licensed whole-cell vaccine.

Antibody responses to PT were dose dependent, being higher in the children who received the monovalent vaccine; FHA antibody rose only in the bivalent vaccine group. Efficacy for both vaccines was less than anticipated (Tables 21-11 and 21-12); for culture-confirmed cough of any duration, efficacy was 69% for the two-component vaccine and 54% for the monocomponent vaccine.[135]

Table 21-11 -- Results of Nine Acellular Pertussis Vaccine Efficacy Trials, Based on Case Definition Most Similar to That of W.H.O.[*]

Efficacy (95% CI)

Vaccine[†] (# Absolute Components) Cases % Relative Risk

Randomized, fully blinded, controlled, Study Case Definition[‡] comparative studies Comment

Stockholm ≥21 days cough + ≥9 JNIH-6 (2) 10 81 (61– Differential sensitivity of 1986[328] coughing spasms on at 90) culture, lack of serologic least 1 day + positive or epi-link criteria may JNIH-7 (1) 12 75 (53– culture bias estimates upwards 87)

Stockholm ≥21 days paroxysmal SKB-2 (2) 159 59 (51– 0.83 (0.66– Because of unusually low 1992[181] cough, plus either: 66) 1.1) vs DTP DTP efficacy, relative positive culture, risks difficult to compare Tripacel[§] (4) 59 85 (81– 0.29 (0.21– confirmed by SA or to other studies 89) 0.40) vs DTP PCR; 2-fold PT or FHA IgG rise; or epi link to Connaught 148 48 (37– culture-positive case DTP 58)

Italy ≥21 days paroxysmal Infanrix (3) 37 84 (76– 0.25 (0.17– Because of unusually low 1992[182] cough, plus either: 89) 0.36) vs. DTP DTP efficacy, relative positive culture, risks difficult to compare Acelluvax (3) 36 84 (76– 0.25 (0.17– confirmed by SA or

44 Efficacy (95% CI)

Vaccine[†] (# Absolute Components) Cases % Relative Risk

Randomized, fully blinded, controlled, Study Case Definition[‡] comparative studies Comment

90) 0.36) vs DTP to other studies

Connaught 141 36 (14– PCR; 4-fold CHO or 2- DTP 52) fold PT or FHA IgG or

IgA rise; no epi-link [§] Stockholm ≥21 days paroxysmal HCPDT (4) 13 0.85 (0.41– Comparison is to the 1993[329] cough plus positive 1.79) vs. DTP Wellcome DTP used in culture (no information this study (see Table 20- Acelluvax (3) 21 1.38 (0.71- on confirmation); no 11). Acelluvax, 2.69) vs DTP serologic or epi-link unchanged from Italy, criteria SKB-2 (2) 99 2.3 (1.5–3.5) provides a link to the Italy study (and thus to Stockholm 1992) ∠ vs DTP

HCPDT[§] (4) 38 0.62 (0.31– 1.2) vs.Acelluvax

SKB-2 (2) 99 2.0 (1.4–2.8) vsAcelluvax|

Randomized, fully blinded, controlled studies

Göteborg ≥21 days paroxysmal Certiva (1) 72 71 (63– Lack of FHA in vaccine 1991 [330] cough plus either: 78) enhanced sensitivity of positive culture serologic criteria, confirmed by SA, PCR; improving accuracy of 3-fold PT or FHA IgG estimate rise; epi link

Other studies

Senegal ≥21 days paroxysmal Triavax (2) 24 74 (51– 2.42 (1.4– Few cases, thus broad 1990[229] cough plus either: 86) 4.3) vs. DTP CIs. Open DT group may

45 Efficacy (95% CI)

Vaccine[†] (# Absolute Components) Cases % Relative Risk

Randomized, fully blinded, controlled, Study Case Definition[‡] comparative studies Comment

positive culture PMC-Fr DTP 7 92 (81– bias absolute efficacy confirmed by DIF; 2- 97) estimates upwards fold PT or FHA IgG rise; epi link

Erlangen ≥21 days cough with ACEL-IMUNE ( ≤45 78 (60– 1.5 (0.7–3.4) Open DT group, 1991[180] paroxysms, whoop, or 4) 88) vs DTP [228] incomplete case vomiting, plus ascertainment may bias Lederle DTP ≤18 93 (83- confirmation[¶] absolute efficacy 97) estimates upwards

Mainz 21 days paroxysmal Infanrix (3) 7 89 (77– 4.7 (0.6– Few cases, thus broad 1992[226] cough plus either: 95) 37.3) vs. DTP CIs. Note how positive culture misleading relative risk is Behring, SKB 1 98 (83– confirmed by DIF or SA; if DTP result is close to DTP 100) 2-fold PT or FHA IgG or 100% IgA rise

Munich 21 days paroxysmal Tripedia (2) 4 93 (63– 2.0 (n/a) vs. Few cases, thus broad 1993[227,331] cough plus either: 99) [#] DTP CIs. Lack of serologic positive culture criteria, blinding, or Behring DTP 1 96 (71– confirmed by SA; epi randomization may bias 100) link; no serologic efficacy estimates criteria upwards

CHO, Chinese hamster ovary cell assay; CI, confidence interval; DIF, direct immunofluorescence; DTP, diphtheria and tetanus tox oids and whole-cell pertussis vaccine; FHA, filamentous hemagglutinin; FIM, fimbrial proteins; IgA, immunoglobulin A; IgG, immunoglobulin G; IgM, immunoglobulin M; n/a, not available or not applicable; PCR, polymerase chain reaction; PMC-Fr, Pasteur Merieux Connaught– France; PMD, private physician; PRN, pertactin; PT, pertussis toxin; SA, slide agglutination; SKB, SmithKline Beecham; WHO, World Health Organization definition.

* Results shown are for complete primary infant immunization series (3 doses, except Stockholm 1986, 2 doses); effects of any booster dose are not included. Some results obtained by recalculation from data provided in the referenced source; such results may represent crude, rather than adjusted, efficacies.

46 Blank cells: not applicable or no data. WHO case definition: ≥21 days paroxysmal cough, plus bacteriologic, serologic, or epidemiologic confirmation that cough is due to B. pertussis.

† Descriptive name given for those without trade name. Letters before hyphen indicate source; characters after hyphen indicate number and type of components. All 1-component vaccines contain PT; all 2-component vaccines contain PT and FHA; 3-component vaccines contain PT, FHA, plus either PRN or FIM (as indicated by the letter P or F respectively); 4-component vaccines contain PT, FHA, PRN, and FIM. are included. See Tables 21-3 and 21-4 for further details.

‡ Unless otherwise noted: All cultures were nasopharyngeal; FHA rises were considered diagnostic only if culture (and PCR, if done) were negative for B. parapertussis; ‘epi link’ confirmed (PCR-confirmed, for Senegal) case within 28 days before or after illness onset in the subject (for Erlangen or Munich, no time limit was specified). Criteria shown are for the case definition most similar to that of the WHO; different criteria may have been used for alternative case definitions.

§ Tripacel and HCPDT are similar, except that Tripacel contains 10 μg PT and 5 μg FHA, as compared to 20

μg of each in HCPDT. ∠For time from 1st dose to soon after the 3rd doses, when SKB-2 recipients were

unblinded and boosted with another vaccine.

¶ Confirmation criteria: Positive culture (confirmed by PCR in last year of study); ‘significant’ PT IgG or IgA result; or household contact to a culture-o of convalescentcase. to acute antibody level that exceeded the 95th, 99th, or 99.9th percentile of a distribution of similar ratios determined among randomly selected subjects at roughly the same time postimmunization. Selection of the percentile limit was determined by how many, and which, antibody ratios were elevated. Efficacy rates reflect adjustment for single adult households and households in which all siblings were unimmunized. Other published efficacy estimates180 may have used FHA, PRN, or FIM IgG or IgA values or 4-fold AGG rises as well, and may not have reflected such adjustment.

# Differs from efficacy reported in FDA-approved patient package insert, which is based on the primary case definition (≥21 days of any cough) rather than the WHO definition.

Table 21-12 -- Results of Nine Acellular Pertussis Vaccine Efficacy Trials for Various Case Definitions or Surveillance Periods[*]

Efficacies (95% CI)

Study Vaccine(s)[†] Case Definition[‡] Absolute, % Relative Risk

Randomized, fully blinded, controlled, comparative studies

47 Efficacies (95% CI)

Study Vaccine(s)[†] Case Definition[‡] Absolute, % Relative Risk

Stockholm JNIH-6, JNIH-7 ≥1 day of any cough + positive 69 (47–82), 54 (26– (1986) culture103 72)

Same; but including cases from 65 (44–78), 53 (28– date of first dose[103] 69)

Same; but for first 60 days after 41 (0–79), 42 (0–79) first dose only[328]

≥1 day cough with spasms 16 (3–27), 5 (− 10, (defined in Table 20-12) 333 17)

≥1 day cough with spasms + ≥1 39 (16–56), 51 (30– day whoops333 65)

≥1 day cough with spasms + 75 (54–86), 60 (33– culture333 76)

≥1 day cough with spasms + 85 (67–94), 89 (72– whoops + culture333 96)

≥21 days cough with 41 (23–55), 27 (6– spasms333 43)

≥21 days cough with spasms + 60 (37–75), 62 (39– whoops333 76)

=21 days cough with spasms + 81 (61–90), 75 (53– culture333 87)

≥21 days cough with spasms + 84 (63–93), 90 (73– whoops + culture333 97)

3 additional years of passive 77 (65–85), 65 (50– surveillance: positive culture239 75)

3 additional years: ≥30 days 92 (84–96), 79 (67– cough + positive culture239 87)

3 additional years: ≥9 cough 89 (76–97), 82 (67– spasms/day + positive 90) culture239

48 Efficacies (95% CI)

Study Vaccine(s)[†] Case Definition[‡] Absolute, % Relative Risk

Stockholm SKB-2,Tripacel ≥21 days paroxysmal cough, 59 (51–66), 85 (81– 0.83 (0.66-1.1), (1992) confirmed as in Table 20-12[181] 89) 0.29 (0.21-0.40) vs DTP

Same; but including cases from 59 (51–66), 84 (80– 0.83 (0.66–1.1), date of first dose[181] 88) 0.30 (0.22–0.42) vs. DTP

≥1 day any cough, confirmed 42 (33–51), 78 (73– as in Table 20-12 181 82)

≥21 days any cough, confirmed 54 (46–62), 81 (76– as in Table 20-12 334 85)

Italy Infanrix,Acelluvax ≥21 days paroxysmal cough + 85 (n/a), 87 (n/a) positive culture[182]

≥21 days paroxysmal cough, 84 (76–89), 84 (76– 0.25 (0.17–0.36), confirmed as in Table 20-12[182] 90) 0.25 (0.17–0.36) vs. DTP

Same; but including cases from 82 (73-87), 84 (76– 0.28 (0.20–0.39), date of first dose[182] 89) 0.25 (0.17–0.36) vs. DTP

Same; but from 30 days after 1st19 (0–84), 83 (0–98) 0.49 (0.17–1.44), dose to 29 days after 3rd[182] 0.10 (0.01–0.79) vs. DTP

≥7 days any cough, 71 (60-78), 71 (61– 0.38 (0.30–0.49), confirmation as above182 79) 0.38 (0.29–0.48) vs DTP

≥21 days any cough, 79 (70–85), 77 (68– 0.29 (0.21–0.39), confirmation as above182 84) 0.31 (0.24–0.42) vs. DTP

Stockholm HCPTD,Acelluvax Positive culture, with or without 1.40 (0.78–2.52), (1993) (±) cough[329] 2.55 (1.50–4.33) vs DTP

≥21 days paroxysmal cough + 0.85 (0.41–1.79),

49 Efficacies (95% CI)

Study Vaccine(s)[†] Case Definition[‡] Absolute, % Relative Risk

positive culture[329] 1.38 (0.71–2.69) vs. DTP

Positive culture, ± cough; from 1.25 (0.90–1.75), date of first dose[329] 1.84 (1.36–2.51) vs. DTP

≥21 d paroxysmal cough + 1.25 (0.82–1.89), positive culture; from first 1.65 (1.12–2.45) vs. dose[329] DTP

Same; but from date of first 1.49 (0.80–2.77), dose to date of second dose[335] 1.42 (0.76–2.65) vs. DTP

Same; but from date of second 1.42 (0.54–3.74), dose to date of third dose[329] 3.14 (1.34–7.34) vs. DTP

Randomized, fully blinded, controlled studies

Göteborg Certiva ≥7 days any cough, confirmed 54 (43–63) as in Table 20-12[330]

≥7 days any cough, confirmed 62 (51–70) by Göteborg criteria[330]

≥21 days any cough, confirmed 63 (52–71) as in Table 20-12[330]

≥21 days any cough, confirmed 69 (60–77) by Göteborg criteria[330]

≥21 days paroxysmal cough, 77 (69–83) confirmed by Göteborg criteria[330]

Same; from 30 days after 2nd 39 (0–66) dose to 29 days after 3rd 336

≥21 days paroxysmal cough, 71 (63–78) confirmed as in Table 20-12[330]

50 Efficacies (95% CI)

Study Vaccine(s)[†] Case Definition[‡] Absolute, % Relative Risk

Same; from first dose to 29 days ≤16 (0–≤64) after second dose[330]

Same; from 30 days after 2nd 55 (12–78) dose to 29 days after 3rd[330]

Same; from 18.5 to 24.5 months 77 (65–85) after third dose[337]

Other studies

Senegal Triavax ≥21 days any cough, confirmed 31 (7–49) 1.54 (1.23–1.94) vs. as in Table 20-12[229] DTP

As above, plus epi-link cases 53 (23–71) 1.87 (1.38–2.52) vs. confirmed by PCR[229] DTP

≥8 days paroxysmal cough, 3.26 (2.08–5.10) vs. confirmed as in Table 20-12[338] DTP

≥21 days paroxysmal cough, 74 (51–86) 2.42 (1.35–4.34) vs. confirmed as in Table 20-12[229] DTP

As above, plus epi-link cases 85 (66–93) 2.80 (1.36–5.74) vs. confirmed by PCR[229] DTP

Erlangen ACEL-IMUNE ≥7 days any cough, confirmed 62 (38–77) [§] 3.1 (n/a) vs DTP as in Table 20-12[180]

≥21 days paroxysmal cough, 78 (60–88) 1.5 (0.7–3.4) vs. confirmed as in Table 20-12[180] DTP

Mainz Infanrix ≥1 day paroxysmal cough[226] 64 (51–73)

≥7 days paroxysmal cough, 81 (68–89) confirmed as in Table 20-12[226]

≥21 days paroxysmal cough, 83 (71–90) with or without confirmation[226]

≥21 days paroxysmal cough, 89 (77–95) 4.7 (0.6–37.3) vs. confirmed as in Table 20-12[226] DTP

51 Efficacies (95% CI)

Study Vaccine(s)[†] Case Definition[‡] Absolute, % Relative Risk

Munich Tripedia ≥21 days any cough, confirmed 4.0 (n/a) vs. DTP ∠ as in Table 20-12[227] 80 (63–89) [ ]

≥21 days paroxysmal cough, 93 (63–99) 2.0 (n/a) vs. DTP confirmed as in Table 20-12[227]

CI, confidence interval; DTP, diphtheria and tetanus toxoids and whole-cell pertussis vaccine; FHA, filamentous hemagglutinin; FIM, fimbrial proteins; HCPDT, hybrid component pertussis-diphtheria- tetanus vaccine; n/a, data not available; PMC-Fr, Pasteur Merieux Connaught–France; PRN, pertactin; PT, pertussis toxin; SB, SmithKline Beecham.

* Results shown are for complete primary infant immunization series (3 doses, except Stockholm 1986, 2 doses); effects of any booster dose are not included. Some results obtained by recalculation from data provided in the referenced source; such results may represent crude, rather than adjusted, efficacies. Lower confidence limits less than zero are shown as zero. Blank cells: not applicable or no data. WHO case definition: ≥21 days paroxysmal cough, plus bacteriologic, serologic, or epidemiologic confirmation that cough is due to B. pertussis. See Tables 21-7, 21-8 for additional details, including confirmation methods used by each study.

† Descriptive name given for those without trade name. Letters before hyphen indicate source; characters after hyphen indicate number and type of components. All 1-component vaccines contain PT; all 2-component vaccines contain PT and FHA; 3-component vaccines contain PT, FHA, plus either PRN or FIM (as indicated by the letter P or F respectively); 4-component vaccines contain PT, FHA, PRN, and FIM. are included. See Tables 21-3 and 21-4 for further details.

‡ Definition most similar to that of the WHO (≥21 days paroxysmal cough, confirmed as pertussis by culture, serology, or epidemiologic link to a culture-confirmed case) is sh own in boldface; see Table 20- 12 for details. Göteborg criteria: Positive culture; or IgG against both PT and FHA ≥6000 in a single convalescent specimen; or two major criteria; or one major and one minor criterion. Major criteria: 3- fold rise in PT or FHA IgG; household contact with confirmed pertussis. Minor criteria: 3-fold change in PT or FHA IgA or IgM; positive PCR. Unless otherwise specified, subjects were eligible for inclusion as cases from time of last dose (Stockholm 1992, Stockholm 1993), from 28–30 days after last dose (Stockholm 1986, Italy, Göteborg, Senegal, Mainz), or from 14 days after last dose (Erlangen) of DTa P (see Table 20-11 for vaccination schedule).

§ Not adjusted for single-adult households and households in which all siblings were unimmunized (see Table 20-12).

52 ∠This result, which is based on the primary case definition rather than the WHO definition, is the one reported in the FDA-appro ved patient package insert.

During the surveillance period, four vaccinees (one JNIH-7 and three JNIH-6 recipients) died of bacterial infections.[390] Review of hospitalizations for infection found no differences among the study groups. Analyses of immunoglobulins from prevaccination and postvaccination sera showed no abnormalities, nor did leukocyte counts obtained in a subsample of subjects 2–4 months after the second dose.

In January 1989, the Swedish National Bacteriology Laboratory withdrew the acellular vaccine licensure application, citing both the impression that efficacy was lower than that of whole-cell vaccines and the possible association with deaths resulting from serious bacterial infections. The laboratory called for studies that would directly compare acellular and whole-cell vaccines.[391]

In light of these safety concerns and of animal data suggesting that PT might enhance the susceptibility of animals to bacterial infection,[392] several studies were conducted that demonstrated, if anything, a decreased risk of severe invasive bacterial disease after DTP immunization[392–395] and no increased risk of minor infections.[394] Data from Japan indicated that there was no enhanced risk from the acellular vaccines.[396] Thus it appeared that the four deaths were chance events, with no causal relationship to vaccination.

Subsequent follow-up and analyses

Later evaluations of various case definitions and confirmatory criteria showed that the two-component and monocomponent vaccines were 81% and 75% effective, respectively, in preventing culture- confirmed disease with at least 21 days of coughing spasms.[397] Estimates of efficacy were profoundly influenced by case definition, ranging (using the monocomponent vaccine as an example) from 5% efficacy in preventing spasmodic cough lasting 1 day or longer to 100% efficacy in preventing culture- confirmed pertussis with spasmodic cough lasting 28 days or longer, with whoops on at least 1 day.[397]

It was also found that prior receipt of pertussis vaccine reduced the likelihood of positive pertussis cultures or significant antibody rises in patients with cough. Thus pertussis infection could be confirmed more readily in placebo recipients than in vaccinees, which tended to bias efficacy estimates upward.

Although the initial results from the 1986 Swedish trial suggested that the efficacies of the monocomponent and two-component vaccines did not differ, long-term follow-up showed the two- component vaccine to be significantly more efficacious (Fig. 21-4).[298] Following unblinding of the study after 15 months of active observation, passive surveillance continued for 3 additional years, during which vaccine efficacy ranged from 77 to 92% for the bivalent vaccine and from 65 to 82% for the monovalent vaccine, depending on the case definition (see Table 21-12).[298] Clinical protection after acellular pertussis vaccine was maintained for at least 4 years.[298]

Figure 21-4 Cumulative incidence curves for culture-confirmed pertussis during unblinded post- trial follow-up, in the placebo group (solid line), in the monocomponent (JNIH-7) vaccine group

53 (dashed line), and in the two-component (JNIH-6) vaccine group (dotted line). Unblinded follow- up started August 27, 1987, and ended September 9, 1990. (From Storsaeter J, Olin P. Relative efficacy of two acellular pertussis vaccines during three years of passive surveillance. Vaccine 10:142–144, 1992, with permission.)

The monocomponent vaccine, with 50% more PT, appeared to be more effective than the two- component vaccine in preventing the most severe manifestations of disease. Its efficacy exceeded that of the two-component vaccine for every case definition involving whoops (see Table 21-12), a difference that was statistically significant for 28 or more days of cough with whoops.[397] On the other hand, the two-component vaccine appeared to be more effective in preventing mild or moderate disease (e.g., shorter durations of cough or cough without whoops).[298,383,398,399] Thus efficacy was influenced by both the choice of antigens and the quantity of antigen included.

The initial efficacy results[135] gave the impression that the acellular vaccines were substantially less efficacious than whole-cell vaccine.[135,298,399]As a result, Japan remained the only country in which they were licensed. However, results of later studies suggest that efficacy would have been higher had a standard three-dose schedule been used. Most important, inclusion of a whole-cell control group might have led to markedly different conclusions regarding the relative efficacy of these vaccines.

World Health Organization case definition of pertussis

In response to the demonstration in the 1986 Swedish trial of the strong influence of pertussis case definitions on estimates of vaccine efficacy, and in expectation of the efficacy trials that would be conducted to evaluate the new vaccines being developed, the WHO convened a group of pertussis experts in January 1991 to develop a consensus case definition of pertussis for use in clinical trials. The resulting WHO case definition required the presence of paroxysmal cough for at least 21 days plus confirmation that the cough illness actually was due to pertussis. This confirmation could be based on laboratory results (e.g., a positive culture for B. pertussis or a significant rise in a specific antibody, such as IgG or IgA against PT, FHA, or FIM-2 or -3) or on an epidemiologic link (e.g., a household contact with a laboratory-confirmed case within 28 days before or after the onset of illness in the subject).[400] The consensus statement recognized that future laboratory developments might add to the tools available for bacteriologic or serologic confirmation (e.g., DFA, PCR, assay of antibody to PRN).

Although the WHO case definition played an essential role in improving comparability of subsequent field trials, its limitations must be recognized. First, it improved but did not eliminate the problem of differential sensitivity of the case definition with respect to detecting pertussis in the various arms of a comparative trial. The yield of positive pertussis cultures was lower in immunized than in unimmunized pertussis patients and varied inversely with the efficacy of the vaccine.[229,398,401–403] Thus a cough illness that was really pertussis was more likely to be confirmed by culture in the unvaccinated group than in the vaccinated group. This disparity led to a disproportionate discarding of true pertussis cases in the vaccinated group, which resulted in falsely elevated estimates of vaccine efficacy. Similarly, the

54 differences between a less effective and a more effective vaccine were likely to be exaggerated because more cases will be confirmed by culture in the group that received the less effective vaccine. Those subjects who already had a substantial increase in the level of a pertussis antibody, as a result of the receipt of a highly immunogenic vaccine, were less likely to show a fourfold (or other diagnostic) rise in antibody titers after infection than those subjects who did not receive a vaccine containing that antigen (or a vaccine substantially less immunogenic with respect to that antigen).[398,403] When comparing two vaccines, one which stimulates the antibody being tested and one which does not, there will be a diagnostic bias favoring the vaccine that stimulates the antibody. If both vaccines contain the antigen in question, the bias will favor the more immunogenic vaccine.

Second, setting the clinical cutoff at ‘paroxysmal cough of 21 days or more’ has been shown to result in the removal of a substantial number of laboratory-confirmed pertussis cases from efficacy calculations. [298,397,404] Because mild cases are more common in vaccinees than in control subjects, it might be argued that the effect is to inflate efficacy estimates, reducing the ability to discriminate among vaccines. However, if one's intent is to measure the vaccine's efficacy in preventing classical whooping cough, and mild disease is of lesser interest, then this quality is not a defect.

Third, the case definition permits the use of a variety of serologic assays for confirmation as well as the future use of additional serologic assays or other bacteriologic techniques to detect B. pertussis organisms. Although commendable, this flexibility means that studies that differ in the laboratory tools employed for case confirmation, and thus in the sensitivity and specificity of case confirmation, nonetheless may characterize themselves as using the WHO case definition. Thus, as always, the burden is on the reader to consider carefully the methods employed in each trial.

Efficacy trials, 1992–1997

After the 1986 Swedish clinical trial, worldwide efforts to develop additional acellular pertussis vaccines continued, culminating in eight additional efficacy trials initiated between 1990 and 1993 (see Table 21- 10). Four of the trials were randomized, prospective, and fully blinded; of these, three incorporated a whole-cell control arm and evaluated several candidate acellular vaccines head to head. The four remaining trials each evaluated only a single vaccine, using a variety of study designs; all made use of placebo (DT or no vaccine) groups that were neither randomized nor fully blinded.

Key characteristics of all nine efficacy studies are summarized in Tables 21-11 and 21-12. For each trial, Table 21-11 presents results for the case definition that we consider most similar to the WHO standard case definition, and Table 21-12 presents selected results reflecting a variety of alternative case definitions or surveillance intervals. For studies not incorporating a placebo control group (e.g., DT), only relative risks (usually calculated relative to a DTP vaccine used in the same trial) are available. However, relative risks must be interpreted with great caution, and can be directly compared across trials only if the reference (e.g., DTP) vaccines are identical. Unfortunately, no two studies conducted without placebo control groups incorporated a common DTP vaccine, and thus relative risks can be compared meaningfully only within the studies that evaluated multiple acellular vaccines.

Sweden and Italy, 1992–1993

55 Of the 13 acellular vaccines evaluated in the MAPT, four were selected, based on evaluations of their safety, immunogenicity, and purity, for evaluation in two NIAID-funded efficacy trials conducted in Sweden and Italy.[229,230] These two NIAID-sponsored studies were of rigorous design and served as the benchmarks against which others were compared. The studies were prospective, double blinded, and randomized and incorporated both placebo (DT) and whole-cell control arms. The two studies used closely coordinated protocols, serologic assays, and case definitions (however, the Italian case definition did not include epidemiologically linked cases, and pre-exposure sera were not collected routinely in Italy as they were in Sweden). Infants were immunized at 2, 4, and 6 months of age, and no booster was given. Each study compared two candidate acellular vaccines head to head. The control whole-cell vaccine used in both was produced by Connaught Laboratories (Swiftwater, PA) and was licensed for use in the United States.

During the main follow-up period of the Swedish study (hereafter referred to as Stockholm 1992), 737 cases of pertussis were diagnosed that met the primary case definition. Efficacy was 59% for the SmithKline Beecham bivalent vaccine (SKB-2), 85% for the Aventis Pasteur five-component vaccine (Tripacel) and 48% for the Connaught whole-cell vaccine (see Table 21-11).[229] The efficacy of the five- component vaccine was sustained during the 2 years of follow-up, whereas the efficacy of the whole-cell vaccine declined substantially.

The performance of the two-component vaccine was much lower than had been anticipated. (JNIH-6, a similar vaccine, was 81% effective in the 1986 trial, using the most similar case definition.) It was noted that the SmithKline Beecham two-component vaccine produced significantly less antibody to PT in Sweden than it had in the MAPT,[405] prompting both the investigators[229] and other reviewers[405] to speculate that the vaccine's performance in Stockholm 1992 may, in part, have reflected characteristics unique to the batch of vaccine used in that trial.

The five-component vaccine was 78% effective against laboratory-confirmed pertussis with at least 1 day of cough, suggesting substantial protection against mild or atypical pertussis. In contrast, for this case definition the two-component and Connaught whole-cell vaccines were 42% and 41% effective, respectively.[229]

During the main follow-up period of the Italian trial, 288 cases of pertussis met the primary case definition. The GlaxoSmithKline (Infanrix) and Chiron Vaccines (Triacelluvax) three-component acellular vaccines were both 84% effective; efficacy for the Connaught whole-cell vaccine was 36%.[230] After completion of the main follow-up period, unblinded surveillance of the study cohort continued. During the first 9 months of extended follow-up, efficacy of the two vaccines differed significantly: 36 cases were detected among recipients of the GlaxoSmithKline vaccine, as compared with 18 among recipients of the Chiron vaccine (efficacies of 78% and 89%, respectively).[351] However, a more complete analysis that incorporated results through April 1997 found no material differences in long-term efficacy. For the GlaxoSmithKline and Chiron vaccines, respectively, efficacies by year of observation were: 1994, 82.7% and 82.1%; 1995, 81.5% and 85.9%; and 1996, 87.6% and 87.7%.[406] Additional follow-up through 6 years of age has demonstrated continued high efficacy of these vaccines.[407]

56 The similarity in efficacy of the three multicomponent vaccines is noteworthy, particularly given their substantially different compositions (see Tables 21-3 and 21-4). Triacelluvax has only one fifth the PT, one tenth the FHA, and one third the PRN content of Infanrix (but the PT is genetically inactivated, rather than being a toxoided natural protein). The Canadian five-component vaccine, Tripacel, had far less than half the PT, FHA, and PRN of Infanrix but contained FIM-2 and FIM-3. These facts strongly suggest that the efficacy of an acellular pertussis vaccine is influenced by both the choice of components and the particular characteristics of those components.

Sweden, 1993–1996

After completion of the immunization phase of Stockholm 1992 (but before completion of the surveillance phase), the Swedish investigators launched another NIAID-supported prospective, randomized, double-blind trial (henceforth referred to as Stockholm 1993) that compared four vaccines: (1) the two-component SmithKline Beecham vaccine evaluated in Stockholm 1992; (2) a five-component Aventis Pasteur Canada vaccine (HCPDT) similar to the one evaluated in Stockholm 1992 (Tripacel) but reformulated to contain more PT and FHA; (3) the three-component Chiron acellular vaccine (Triacelluvax) evaluated in Italy; and (4) a different whole-cell vaccine, the Medeva Wellcome whole-cell vaccine (now produced by Evans Medical) used in the United Kingdom.[408] Because of the safety and efficacy of acellular pertussis vaccine demonstrated in Stockholm 1992, Stockholm 1993 did not incorporate a placebo group. Conducted in 22 of 25 Swedish counties, the trial randomized 82,892 children to be immunized at 3, 5, and 12 months of age (the Swedish schedule for DT). Surveillance was predominantly passive; detected rates of pertussis were markedly lower than in Stockholm 1992. Surveillance was terminated early for the group receiving the two-component SmithKline Beecham vaccine, and the subjects were immunized with the Canadian five-component acellular vaccine when results from the Stockholm 1992 study showed the two-component vaccine to be of substantially lower efficacy than the others.

The relative performances of the evaluated vaccines are shown in Tables 21-11 and 21-12 (the absence of a placebo control group precludes calculation of absolute vaccine efficacies). Relative risks of culture- confirmed B. pertussis infection with at least 21 days of paroxysmal cough were 0.85 and 1.38 for the five-component and three-component vaccines, respectively, as compared with whole-cell vaccine. The relative risk of pertussis occurring between administration of the second dose (5 months of age) and third dose (12 months of age) of vaccine was 1.42 for the five-component vaccine, 3.13 for the three- component vaccine, and 7.81 for the two-component vaccine (as compared with whole-cell vaccine). Efficacy of the two-component vaccine differed significantly from that of the other three.

The Stockholm 1993 study provides important new data, but several factors complicate the direct comparison of its results to those of other trials. As noted, there was no placebo control group, precluding calculations of absolute efficacy. The Wellcome whole-cell vaccine was not used in any other efficacy trial. The five-component Aventis Pasteur Canada vaccine evaluated was the ‘hybrid’ formulation developed for use in combination vaccines, containing twice the PT and four times the FHA as in the ‘classical’ formulation. The SmithKline Beecham two-component vaccine was used in

57 Stockholm 1992, but surveillance of this group was terminated early in the second Stockholm study. Thus the Chiron three-component vaccine represents the only link to the prior trials.

Based on the Stockholm 1992 and Italy 1992 trials (see Table 21-11), Infanrix, Triacelluvax, and the classical (CLL-4F2) formulation of Tripacel appear to be of equal efficacy. In Stockholm 1993, however, the relative risk of typical pertussis with the reformulated (hybrid or HCPDT) version of Tripacel was 0.62 (95% CI, 0.28–1.29) compared to Triacelluvax. For combined mild and severe pertussis, the hybrid five- component vaccine was equal to the whole-cell vaccine but significantly better than Triacelluvax. [409] Taken together, these observations suggest that the hybrid formulation of Tripacel is more efficacious than the classical formulation, and accordingly, that increasing the amount of PT and FHA in a vaccine can increase its efficacy. Of note, serologic studies performed on small subsets of subjects in the 1992[401] and 1993[403] Stockholm trials found significantly higher FHA responses with the hybrid formulation used in 1993 compared with the classical formulation used in 1992. There were no differences in antibody responses to the SmithKline Beecham bivalent vaccine lots used in the 1992 and 1993 trials.

Göteborg, Sweden

A randomized, double-blind, placebo-controlled trial sponsored by the National Institute of Child Health and Human Development (NICHD) was conducted in Göteborg, Sweden, from September 1991 to July 1994. This trial evaluated the monocomponent (PT toxoid only) acellular vaccine (Certiva) developed by the NICHD and manufactured at that time by North American Vaccine.[410] Children were immunized with DTaP or DT at 3, 5, and 12 months of age; there was no whole-cell control group.

During the period from 30 days after the third (12-month) vaccination to the end of the study, 72 DTaP and 240 DT recipients met the WHO case definition, for an efficacy of 71%. Other case definitions produced efficacy estimates ranging from 54 to 77%, depending on the stringency of the definition. A nested analysis of subjects with household exposure to pertussis found 66% efficacy after two doses and 75% efficacy after three doses.[411] During an additional 6 months of surveillance after unblinding of the study (representing a period averaging 18.5 –24.5 months after the third injection), efficacy was 77% for the full cohort and 76% in a nested household-contact study.[403]

Because this vaccine included only PT toxoid, serologic rises of antibodies to FHA were an unbiased indicator of possible pertussis. Thus pertussis could be identified more readily among vaccine recipients than if the vaccine had contained FHA. Other vaccines to which this vaccine is compared may have benefited from a lower case ascertainment rate in the vaccine groups, biasing their efficacy estimates upward.

The only other efficacy trial that immunized subjects at 3, 5, and 12 months of age was Stockholm 1993. However, comparing results with that study cannot readily be done; the two studies evaluated no acellular vaccines in common, and there was no DT arm in Stockholm 1993 or whole-cell arm in Göteborg.

58 Follow-up for 2 years following immunization showed no diminution in protection among the DTaP group, as compared to the DT group.[403]Subsequent mass immunization in the Göteborg area using the PT toxoid vaccine resulted in significant decreases in B. pertussis isolates and hospitalizations in all age groups.[412]

Munich, Germany

An unblinded, nonrandomized case-control study sponsored by Sanofi Pasteur was conducted in 63 German pediatric practices from February 1993 to May 1995.[286] A cohort of children was enrolled prospectively to receive, according to parental choice, either the Aventis Pasteur-Biken two-component DTaP (Tripedia), the Behringwerke DTP, a DT vaccine, or no vaccine at approximately 3, 5, and 7 months of age.

All infants 2–24 months of age who presented to a participating pediatrician with cough for 7 days or more, or with suspected exposure to pertussis, had nasopharyngeal specimens obtained for culture (whether the children were part of the above cohort or not). There were 11,237 such children, including 3,245 who were part of the prospective cohort. Children whose cultures were positive and whose cough persisted for 21 days or more were each matched with four control patients from the same practice who were born within 30 days of the subject. Pertinent clinical, demographic, and immunization data were entered into a conditional logistic regression analysis to calculate the relative odds of pertussis while controlling for confounding factors.

Eighty-seven subjects met the case definition of 21 or more days of paroxysmal cough plus either positive culture or household contact with a laboratory-confirmed case. These individuals were matched to 344 control subjects. Eighty-one of the case subjects and 186 of the control subjects had received no pertussis vaccine; 4 and 55, respectively, had received three doses of DTaP; and 1 and 61, respectively, had received three doses of DTP. Adjusted estimates of efficacy were 96% for the DTP and 93% for the DTaP.[286]

This study raises issues that may be applicable to any study that is not completely blinded and randomized. Although these efficacy estimates reflect adjustment for risk factors that differed between cases and controls, such as the number of siblings in day care, it is not possible to adjust for, or even confirm the existence or magnitude of, any bias that might have arisen because the study was not blinded or randomized. The analysis rested on comparing the proportions of vaccinated patients in two groups: those patients who were brought in because of possible pertussis, and control subjects who were selected in a systematic manner. If unvaccinated children were more likely than vaccinated children to be brought to the pediatrician with suspicious cough, they would be over-represented in the case (but not control) groups, biasing upward the estimates of efficacy for DTaP and DTP.

Could this bias have happened? Parents knew what vaccine their child received; those whose child received no pertussis vaccine might have been more likely to seek care when their child had a cough illness. (Conversely, parents who selected a pertussis-containing vaccine may have been more health conscious and more likely to seek medical attention than other parents. Lack of blinding can bias in either direction.) It is reassuring that 76% of cultures in the prospective cohort were from infants

59 receiving DTaP, and infants receiving DTaP comprised 75% of the cohort, suggesting that any bias was negligible.

Even if the parents did not differ in their response to cough illness, we know that vaccinated children who develop pertussis have a milder illness. Such children are less likely to have been brought to the pediatrician and are thus less likely to have been included in the case group. Because the case definition did not allow for serologic confirmation of possible cases, confirmation depended on obtaining a positive culture, thus increasing the risk of diagnostic bias (as described after the 1986 Swedish trial).

These factors, coupled with the small number of cases detected, led us to interpret the point estimates of efficacy from the Munich trial with caution. Some reassurance, however, is derived from the fact that the Munich and Mainz studies generated similar estimates of efficacy for the referent whole-cell vaccine that was common to both.

The Munich investigators continued to follow the study cohort through the end of 2001. During the period from 2 years through 6 years (1997–2001) following the fourth dose of pertussis vaccine (given at 15–24 months of age), the crude overall efficacy against typical pertussis (defined as 21 or more days of paroxysmal cough) was 93% (95% CI, 79–98%) for those receiving Tripedia and 96% (95% CI, 76–99%) for those receiving the Behring whole-cell vaccine; adjusted for various confounders, the respective efficacies were 96% (85–99%) and 97% (81–99.6%). Protection was materially lower among those not receiving four doses: crude and adjusted efficacies for those receiving three or fewer doses of Tripedia were 82% (7–96%) and 83% (-5 to 97%), respectively. Adjusted efficacy against milder pertussis (defined as 7 or more days of any cough) was 71% (45–84%) for those receiving four doses of Tripedia and 80% (40–93%) for those receiving four doses of Behring whole-cell vaccine. (Note that long-term follow-up results from the various efficacy trials should not be compared directly to the results obtained in the original trials, given the substantial differences in surveillance methods and sensitivities.)

Erlangen, Germany

A prospective, randomized, double-blind clinical trial conducted from May 1991 to December 1994 in Erlangen, Germany, compared two vaccines produced by study sponsor Wyeth-Lederle: the Lederle- Takeda four-component DTaP (ACEL-IMUNE) and the U.S. DTP that served as the control vaccine in the MAPT.[228,287] Participants were immunized at approximately 3, 5, 7, and 17 months of age. Infants whose parents declined pertussis immunization received a German DT vaccine at approximately 3, 5, and 17 months of age and served as the control group for estimates of absolute efficacy.

Based on a case definition of 21 or more days of cough with paroxysms, whoop, or post-tussive vomiting plus either positive culture, positive serology, or household contact with a culture-proven case, efficacies after three doses of vaccine were 78% for DTaP and 93% for DTP.[228] (The abstract of this trial's published report cites an efficacy of 83% for the DTaP, but that figure reflects the benefit of a fourth, booster dose of vaccine and thus is not comparable to the data presented for the other trials.) As reported in the FDA-approved labeling for ACEL-IMUNE, the relative risk of pertussis was 1.5 for DTaP compared with DTP.[287] A household-contact study nested within the overall trial found efficacy rates similar to those reported from the cohort study.[413]

60 Although this study also used an unblinded, nonrandomized placebo control group for estimates of absolute efficacy, the potential for ascertainment bias may have been reduced by the use of active surveillance (telephone calls every 2 weeks) to detect possible cases. In a follow-up analysis that has implications for all of the efficacy studies, the local physicians who served as study investigators were stratified into three groups based on the proportion of their patients who underwent investigation for pertussis.[414] For subjects attended by physicians who sought pertussis diligently, efficacy of the DTaP in preventing laboratory-confirmed pertussis with 7 or more days of cough was only 40%, whereas efficacy was 78% and 75% in the physician groups of moderate and low diligence, respectively. These results are not surprising, in that the less diligent physicians detected only the more obvious (i.e., more severe) cases, and it has long been known that the efficacy of pertussis vaccine appears higher when one uses case definitions that focus on more severe disease. Nonetheless, this analysis has illuminated the extent to which fairly subtle differences in diagnostic diligence can alter estimates of efficacy, and it alerts us to another factor that might confound efforts to compare the results of different studies.

The Lederle–Takeda acellular vaccine was a four-component vaccine, but it predominantly consisted of FHA (86%; about 35 μg), with very little PT, fimbrial proteins, or PRN, as reflected by both its formulation (see Table 21-3) and its immunogenicity (see Table 21-8). It appeared to be of somewhat lower efficacy than the three-component vaccines evaluated in Italy (although the 95% CIs do overlap). If so, this represents further evidence that the quantity of the individual components can be as important as the number of components in determining the efficacy of the vaccine.

Following unblinding of the study, physicians and parents of approximately one third of study participants agreed to respond to semiannual questionnaires regarding cough illness and pertussis among study participants. Surveillance from 1995 through 2000 showed no diminution in pertussis protection in either the DTaP or the DTP group, as compared to the DT group.[415]

Niakhar, Senegal

A prospective, randomized, double-blind study conducted in Senegal from 1990 to 1994 compared a two-component DTaP produced by study sponsor Aventis Pasteur (Triavax) with that company's European DTP in children immunized at 2, 4, and 6 months of age.[288] Estimates of absolute efficacy were derived from a nested case-contact study that compared rates of pertussis (after exposure to an index case) among study subjects and nonstudy children (who thus had received either DT or no vaccine) living in the same villages and housing compounds. Thus the study design was analogous to that of a household-contact study.

Surveillance detected 197 DTaP and 123 DTP recipients who met the primary case definition of confirmed pertussis (see Table 21-11) with cough for 21 or more days, yielding a relative risk of pertussis 1.54 times higher in the DTaP than the DTP group. Requiring the cough to be paroxysmal (the WHO definition) reduced the case counts to 41 and 16, respectively, for a relative risk with DTaP of 2.42 compared with DTP.

61 When cases were stratified by age, the relative risk of meeting the primary case definition was 1.16 for children younger than 18 months versus 1.76 for older children, suggesting that protection waned more quickly among DTaP than DTP recipients.

The case-contact study included 197 DTaP recipients, 190 DTP recipients, and 17 unvaccinated children exposed to pertussis, of whom 24, 7, and 8, respectively, met the WHO case definition; the absolute efficacy estimates were 74% for DTaP and 92% for DTP. Owing to the small number of cases, confidence limits for these estimates are wide (95% CIs, 51–86% and 81–97% for DTaP and DTP, respectively). In addition, although field surveillance workers and physician evaluators were blinded to the vaccination status of the randomized children, it is obvious that parents knew whether their children had been vaccinated, a situation that may have increased case detection among unimmunized children. For both reasons, the relative rates are likely to be more reliable than the absolute efficacy estimates.

Initial reports from the investigators cited efficacies of 85–86% for DTaP and 95–96% for DTP,[416] and some early reviews echo those figures.[417,418]However, these higher efficacies are based on a requirement that epidemiologically linked cases be confirmed by PCR, a case definition more strict than that of the WHO.

Compared with whole-cell vaccine, relative risks of WHO-defined pertussis were 0.85 and 1.38 in Stockholm 1993 for the five-component Aventis Pasteur and three-component Chiron vaccines, respectively, as compared with 2.42 for the two-component DTaP evaluated in Senegal. Unless the Aventis Pasteur whole-cell vaccine used in the Senegal trial is substantially more effective than the Wellcome whole-cell vaccine used in the Stockholm 1993 trial, it would appear that this two-component acellular vaccine is less efficacious than the three- and five-component vaccines evaluated in Sweden and Italy. (The data do not permit a direct comparison with the two-component vaccine evaluated in Sweden.) As mentioned earlier, breakthrough cases in children immunized with either whole cell or acellular vaccine were less severe and infectious than those in the unimmunized control group.

Mainz, Germany

A prospective household-contact study was conducted from October 1992 to September 1994 in six areas of Germany, in which 22,505 children had been immunized with study sponsor GlaxoSmithKline's three-component acellular pertussis vaccine (Infanrix) in a prior safety and immunogenicity trial. Other children in these regions were unimmunized against pertussis or had been immunized with the Behringwerke whole-cell vaccine at 3, 4, and 5 months of age, in accord with the standard German schedule. Passive surveillance for pertussis identified households that contained both an index case of pertussis and at least one contact age 6–47 months who could be evaluated. Prospective surveillance of the 360 eligible contacts identified 104 secondary cases of pertussis (defined as 21 or more days of spasmodic cough plus either culture or serologic confirmation of B. pertussisinfection): 96 of the 173 unvaccinated children, 7 of the 112 DTaP recipients, and 1 of the 75 DTP recipients. The corresponding estimates of vaccine efficacy were 89% for the DTaP and 98% for the Behringwerke DTP.[285]

The use of a household-contact study design largely eliminated the potential for ascertainment bias that would otherwise arise from the fact that study groups were not blinded or randomized, because family

62 members were intensely surveyed by blinded field supervisors for pertussis in households with an index case. However, the authors noted that the efficacy of the Behringwerke whole-cell vaccine may have been overestimated owing to more frequent erythromycin use among contacts who had received the whole-cell vaccine.[285] The simplest explanation for the higher efficacy estimate for Infanrix in this study (89%) than in the more rigorous, prospective Italian trial (84%) is that the small number of cases in this study reduced the precision of the estimate, as reflected by the wide confidence limits (95% CI, 77– 95%).

Conclusions from the efficacy trials

Although the efficacy trials and other studies have greatly enriched our understanding of pertussis vaccines, they have left many important questions unresolved. Despite attempts to standardize key variables, no two studies are perfectly comparable. For example, as shown in Figure 21-5, not only is the estimate of efficacy affected by case definition (being higher with stricter case definitions), but the various vaccines differ profoundly in the degree to which their efficacies vary with changes in case definition. Moreover, no study has evaluated a multicomponent vaccine directly against versions of itself that contain alternate components or different quantities of each component, and there is no reasonable expectation of such a study. To a considerable extent, however, the issue is moot. Because of the trend toward combination vaccines, the drive to eliminate thimerosal use, and continued consolidation within the vaccine industry there now are only three broadly distributed acellular pertussis vaccines: the French 2-component, Belgian 3-component, and Canadian 5-component vaccines. National surveillance data have clearly demonstrated the ability of each vaccine to accomplish excellent control of pertussis.[100,419]

63 Figure 21-5 Efficacy vs case definition. Efficacy of pertussis vaccines evaluated in prospective, randomized trials (names defined in Table 21-3) for preventing various durations of any cough associated with culture-confirmed pertussis. A slope of zero (horizontal line) would indicate equal protection for mild and severe disease; steeper slopes reflect lesser protection for mild than severe disease. Because estimates were obtained in separate studies, only the slopes, and not the actual values, should be compared. (Michael Decker, used with permission.)

Onset of protection and effect of vaccine schedule

It appears that some protection (perhaps 15–20%) accrues with the first dose, and substantially more with the second dose (see Table 21-13). A reanalysis of data in the Technical Report of the Stockholm 1993 trial indicates that the incidence of pertussis was markedly lower after the second dose than after the first dose, and was reduced somewhat further by the third dose (Table 21-13).[420] These data also illustrate that patterns of protection vary by dose; the whole-cell vaccine offered relatively greater protection with a single dose, lower incremental benefit with the next dose, and a more rapid decline in protection with time following the third dose.

Table 21-13 -- Incidence of Pertussis (Per Million Days at Risk) by Dose, Stockholm 1992 Efficacy Trial[*]

64 Interval SKB-2 Acelluvax HCPDT Evans-Medeva WCV

Primary Analyses (follow-up from study start until October 1996)

Dose 1 to Dose 3 n/a 8.1 6.7 4.4

Dose 3 to study end (approx 21 mos) n/a 1.8 1.1 1.3

Secondary Analyses (follow-up from study start until 28 July 1995, when SKB-2 group was reimmunized with HCPDT)

Dose 1 to Dose 2 19.6 16.0 16.9 11.3

Dose 2 to Dose 3 14.3 5.8 2.6 1.8

Dose 3 to early termination (approx 7 mos) 4.2 1.3 1.0 0.5

* Data derived from Tables 12.1.1, 12.1.3, 12.2.1, 12.2.3, and 12.2.4 in Olin P, Gustafsson L, Rasmussen F, et al. Efficacy tria l of acellular pertussis vaccines: technical report trial II, with preplanned analysis of efficacy, immunogenicity and safety. Swedish Institute for Infectious Di sease Control, Stockholm, 1997.

In general, three doses appear to be necessary for acceptable protection and, for most of the vaccines and schedules, a booster dose at around 15 months of age will provide substantial additional benefit. There is probably little difference between schedules that immunize at ages 2, 4, and 6 months; 3, 5, and 7 months; or even 2, 3, and 4 months. Immunizing at 3, 5, and 12 months of age gives a little less protection in the second half-year of life and better protection thereafter, as one would intuitively expect.

Following conclusion of the efficacy trials, Sweden implemented nationwide acellular pertussis vaccination, using a variety of vaccines in various counties over time. Gustafsson and colleagues have recently reported the results of 7 years of follow-up of national pertussis surveillance. In 2001–2004, pertussis rates/100,000 person-years were 225 in the unvaccinated, 212 after one dose (3 mos), 31 after two doses (5 mos), and 19 after three doses (12 mos). These studies also suggest that the incidence of confirmed pertussis is increasing in children over 6 years of age and suggest that a booster dose is warranted between 5–7 years of age.[421]

Choice of vaccine

For those providers free to choose among vaccines, we recommend consideration of five factors (some may not apply in every situation): efficacy, rate of adverse effects, cost, convenience (e.g., how is the vaccine supplied?), and service (e.g., reliability of supply, provision of educational materials, etc.). Choices can then be made based on the relative weights assigned to each of those factors.

Other evidence of effectiveness of acellular vaccines

65 Both the whole-cell and acellular pertussis vaccines have been highly effective in controlling pertussis in Japan. From 1948 to 1975, pertussis was well controlled by a program that initiated immunization at the age of 3 months (see Fig. 21-6).[267] In response to concerns regarding adverse reactions, in 1975 the age of immunization was raised to 24 months, effectively suspending immunization for 2 years. During this period, reported pertussis cases in Japan rose dramatically, with more than 40,000 cases and nearly 200 deaths for the 8 years from 1976 to 1983.[212,267] By 1980, vaccine acceptance rates were again above 70%, and pertussis cases began to decline.[267] In 1981, whole-cell vaccine was replaced by the new acellular vaccines, and the decline in cases and deaths continued;[267] by 1988, reported pertussis cases were approximately 400, with 5 deaths.[422]

Figure 21-6 Number of reported pertussis cases and deaths, by year, in Japan from 1947 to 1990. ‘New DPT’ refers to the Biken and Takeda-type acellular vaccines (see text). (From Kimura M. Japanese clinical experiences with acellular pertussis vaccines. Dev Biol Stand 73:5–9, 1991, with permission.)

66 It was hoped that a program that vaccinated children beginning at 2 years of age would prevent transmission of disease to younger children,[267] and national surveillance data indeed revealed that pertussis rates declined sixfold to ninefold among unimmunized children younger than 2 years. [423]Unfortunately, even with this decline, 1984 pertussis rates still remained sixfold higher among these unimmunized children than they had been in 1974, prior to the suspension of whole-cell immunization. For children 3 years and older, however, the incidence of pertussis was essentially the same in 1984 as it had been in 1974.[267] Consequently, the national immunization policy was changed once again, and beginning in 1989, it was recommended that pertussis immunization commence at age 3 months.

A later study provided data showing that the incidence of pertussis among children 2 years and younger continued to decline between 1987 and 1989.[269] Thus it would appear that use of the acellular pertussis vaccines among older children was capable of protecting younger, unimmunized children but that the full effect did not appear until vaccination had continued long enough, and widely enough, to substantially reduce overall pertussis rates.

Household-contact studies in Japan found that the efficacy of the acellular vaccines ranged from 78 to 94%.[267,268,424–427] Studies of the Lederle–Takeda[272,320,422,428–435] and Aventis Pasteur-Biken[272,320,436– 438] vaccines found that their immunogenicities were comparable to those of whole-cell vaccine and were similar in Japanese and U.S. infants. In addition, these vaccines caused fewer adverse reactions than the whole-cell vaccine. These data justified licensure of these vaccines in the United States for the fourth and fifth doses, prior to completion of the efficacy trials.[389,439]

An active, nationwide, hospital-based surveillance system in Germany (where acellular vaccines have predominated since their introduction) has demonstrated an age-adjusted effectiveness of completed primary vaccination of 99.8% (95% CI, 98.9–100%) for prevention of hospitalization as a result of pertussis.[440] Even a single dose gave 68% effectiveness.

Duration of immunity after acellular vaccines

The available data from follow-up of various efficacy trial cohorts, covering periods ranging from 2–6 years, show no diminution in protection from pertussis for the evaluated acellular pertussis vaccines, with the single exception of the experimental two-component GSK DTaP evaluated in Sweden.

Long-term follow-up of subjects in the 1986 Swedish efficacy trial did not demonstrate any decline in efficacy of the JNIH-6 or JNIH-7 vaccines through the end of the fourth year after immunization (although it did make clear the higher efficacy of the JNIH-6 vaccine).[298] In the Stockholm 1992 trial, efficacy of the Aventis Pasteur five-component vaccine was sustained above 80% during 2 years of follow-up, whereas that of the control whole-cell vaccine declined sharply.[229] During 6 years of extended follow-up in the Italian trial, efficacies of both the Chiron and the GlaxoSmithKline three- component vaccines were fully maintained.[230,406] Follow-up of subjects given Certiva in the Göteborg trial showed that protection remained unchanged for at least 2 years after the third dose. Follow-up of the Erlangen cohort for 6 years showed no diminution in protection for the Lederle–Takeda DTaP or the Lederle DTP. Five-year follow-up results for the Aventis Pasteur-Biken vaccine used in the Munich cohort also demonstrated persistent protection.

67 Gustafsson and colleagues, in their most recent report of the long-term surveillance of acellular pertussis vaccination in Sweden, found that pertussis incidence remained low for 6 years after vaccination, then rose for those 7 and 8 years old to 32 and 48/100,000 person-years. Based on these findings, they suggest implementation of a booster between 5–7 years of age.[421]

Adverse events with acellular vaccines

Numerous safety and immunogenicity studies of the acellular vaccines have been conducted in infants and children[437,441–446] and have invariably found the acellular vaccines to be associated with lower rates of adverse reactions than whole-cell vaccine. Although most trials have not compared one acellular vaccine with another to detect differences in the rates of adverse reactions, the MAPT evaluated 13 acellular and two whole-cell vaccines and thus offers the best comparison of common reactions with these vaccines.[320] The various efficacy trials maintained surveillance for severe adverse events among much larger numbers of infants and thus supplement the MAPT data by providing more precise estimates of rates for these less common events.

Common adverse events: comparative rates

The MAPT included all acellular vaccines studied in the efficacy trials except one, a monovalent PT vaccine similar to Certiva, produced by North American Vaccine. Fortunately, this vaccine was evaluated using the MAPT protocol in a subsequent trial at one of the MAPT study sites, which allows it to be directly compared with the other vaccines (see Table 21-14). Among the acellular vaccines, there were significant differences with respect to redness, swelling, pain, and vomiting but not fussiness, drowsiness, anorexia, or antipyretic use.[320] No acellular vaccine was consistently the most or least reactogenic. Compared with the reference whole-cell vaccine, all the acellular vaccines were associated with significantly lower rates and severity of every reaction except vomiting.

Table 21-14 -- Adverse Reaction Results From the Multicenter Acellular Pertussis Trial and a Follow- up Trial[*]

68 Reported Incidence of Reaction By the Third Evening Following Vaccination at 2, 4 or 6 Months of Age

# of Values Exceedi ng Crude MAPT Overall DTAP Redness, Swelling, Pain[ FussinesDrowsin Anore Vomiti Averag Averag Fever,°F mm mm ‡] s[§] ess xia ng e[|] e[¶]

Manufactur Vaccine[†100. >101 1– >20 1– >20 er or ] 1– .1 20 20 Distributor 101

SanofiPaste Tripacel 29.2 3.6% 32.8 3.6%21.9 4.4%5.1%18.2% 42.3% 19.0% 12.4% 17.5% 6 ur (Canada) % % %

SanofiPaste 3- 22.4 3.2% 44.0 2.4%22.4 8.0%12.0 21.6% 45.6% 27.2% 21.6% 20.9% 8 ur (Canada) compon % % % % ent

SanofiPaste Triavax 24.1 4.6% 42.9 4.5%28.6 5.3%8.3%12.0% 42.1% 20.3% 7.5% 18.2% 7 ur (France) % % %

SanofiPaste Tripedia 19.3 5.2% 27.4 5.2%16.3 3.7%9.6%19.3% 41.5% 22.2% 7.4% 16.1% 5 ur (USA) % % %

Baxter Certiva 20.0 2.5% 20.0 2.5%7.5%2.5%7.5%22.5% 30.0% 20.0% 2.5% 12.5% 2 Laboratories % %

Biocine 1- 18.6 3.6% 28.3 5.3%24.8 3.5%3.6%20.4% 52.2% 25.7% 17.7% 18.5% 6 Sclavo compon % % % ent

Chiron Acelluva 19.0 1.6% 29.4 1.6%17.5 2.4%1.6%16.7% 41.3% 19.0% 9.5% 14.5% 0 Vaccines x % % %

GlaxoSmith Infanrix 28.3 3.3% 35.0 4.2%24.2 5.8%10.8 15.0% 46.7% 19.2% 12.5% 18.6 7 Kline % % % %

Massachuse 1- 21.2 4.1% 36.3 1.4%21.9 6.2%8.2%16.4% 48.6% 22.6% 14.4% 18.3% 8 tts Public compon % % % Health ent Biologic

69 Reported Incidence of Reaction By the Third Evening Following Vaccination at 2, 4 or 6 Months of Age

# of Values Exceedi ng Crude MAPT Overall DTAP Redness, Swelling, Pain[ FussinesDrowsin Anore Vomiti Averag Averag Fever,°F mm mm ‡] s[§] ess xia ng e[|] e[¶]

Manufactur Vaccine[†100. >101 1– >20 1– >20 er or ] 1– .1 20 20 Distributor 101

Labs

Michigan 2- 22.1 2.2% 30.1 5.9%19.1 3.7%13.2 16.2% 46.3% 23.5% 14.0% 17.8% 5 Department compon % % % % of Public ent Health

SmithKline 2- 18.8 3.1% 31.3 2.1%23.4 4.2%6.2%17.2% 37.0% 17.7% 10.9% 15.6% 2 Beecham compon % % % Biologicals ent

Speywood 3- 17.6 5.0% 36.1 2.5%21.0 4.2%4.2%24.4% 45.4% 18.5% 10.9% 17.3% 5 (Porton) compon % % % Pharmaceutient cals

Wyeth 3- 16.0 5.9% 15.1 2.5%10.9 0.8%5.9%12.6% 29.4% 22.7% 12.6% 12.2% 2 Lederle compon % % % Vaccines ent and Pediatrics

Wyeth ACEL- 16.6 3.2% 23.5 2.8%12.4 3.2%3.7%14.3% 40.6% 24.9% 13.4% 14.4% 2 PharmaceutiIMUNE % % % cals

70 Reported Incidence of Reaction By the Third Evening Following Vaccination at 2, 4 or 6 Months of Age

# of Values Exceedi ng Crude MAPT Overall DTAP Redness, Swelling, Pain[ FussinesDrowsin Anore Vomiti Averag Averag Fever,°F mm mm ‡] s[§] ess xia ng e[|] e[¶]

Manufactur Vaccine[†100. >101 1– >20 1– >20 er or ] 1– .1 20 20 Distributor 101

Average for — 20.8 3.7% 31.4 3.3%20.1 4.2%6.9%17.1% 42.7% 21.7% 12.6% 16.8% 5 all DTaPs in % % % MAPT

Wyeth Whole- 44.5 15.9 56.3 16.4 38.5 22.4 40.2 41.5% 62.0% 35.0% 13.7% — — Lederle cell % % % % % % % Vaccines and Pediatrics

Adapted with permission from Decker MD, Edwards KM, Steinhoff MC, et al. Comparison of 13 acellular pertussis vaccines: adverse reactions. Pediatrics 96:557–566, 1995.

CI, confidence interval; FHA, filamentous hemagglutinin; FIM, fimbrial proteins; MAPT, Multicenter Acellular Pertussis Trial; P RN, pertactin; PT, pertussis toxin.

* Results for Certiva are from a separate study conducted at an MAPT study center after completion of the MAPT, using the MAPT protocol, procedures, and data forms.

† Number of pertussis components, for those vaccines without known trade names. For branded products, note that the licensed vaccine's formulation may differ from that footnotes for details.

‡ Moderate (cried or protested to touch) or severe (cried when leg moved).

§ Moderate (prolonged crying and refused to play) or severe (persistent crying and could not be comforted).

| An unweighted average of the 11 specific rates shown to the left of this value. Has the effect of giving

71 more weight to less se rious reactions, but provides a crude overall comparison that may be useful.

¶ Of the 11 specific rates, the number for which this vaccine's reaction MAPT (see the next-to-last row of the table). Treats small differences and large differences as thoughrate exceeded the average for all DTaPs evaluated in the they were the same, but provides a crude overall comparison that may be useful.

Common and severe adverse events: data from the efficacy trials

Adverse reaction data from the efficacy trials, organized by vaccine, are summarized in Table 21-15. Definitions and methods may have differed from study to study, and thus caution should be used in comparing rates between trials. Note also that Table 21-15 presents reaction rates per dose of vaccine, whereas the rates presented in the following paragraphs are per subject (these two approaches will produce different rates unless every child with a reaction has the same reaction with every dose). Detailed information is provided only for currently available products; readers desiring information regarding other products are referred to the fourth edition of this text.[447]

Table 21-15 -- Incidence (Per 1000 Doses) of Major Adverse Reactions Following Primary Immunization: Data from Efficacy Trials, 1992–1997[*]

Product Trial Vaccine Doses High Fever[†] HHE Persistent Crying Seizures[§]

ACEL-IMUNE Erlangen[180] DTaP 16,644 0.06 0 2.0[‡] 0.06

DTP 16,424 0.19 0.06 8.8[‡] 0.18

Tripedia Munich[227] DTaP 41,615 n/a[†] 0.05 0.12 0.02

Infanrix Italy[182] DTaP 13,761 0.36 0 0.44 0.07

DTP 13,520 2.4 0.67 4.0 0.22

DT 4,540 0.44 0.44 0 0

Acelluvax Italy[182] DTaP 13,713 0.29 0.07 0.66 0

DTP 13,520 2.4 0.67 4.0 0.22

DT 4,540 0.44 0.44 0 0

Stockholm 1993[329] DTaP 61,219 0.24 0.26 n/a 0.03

DTP 60,792 0.61 0.56 n/a 0.21

72 Product Trial Vaccine Doses High Fever[†] HHE Persistent Crying Seizures[§]

Certiva Göteborg [330] DTaP 5,124 2.6 0 0[‡] 0.4

DT 5,130 1.9 0 0[‡] 0

Tripacel Stockholm 1992[181,334] DTaP 7,699 0.26 0.13 0.9 0

DTP 6,143 4.4 0.81 4.8 0.16

DT 7,667 0.39 0 0.52 0.26

HCPDT Stockholm 1993[329] DTaP 61,220 0.11 0.47 n/a 0.06

DTP 60,792 0.61 0.55 n/a 0.21

Triavax Senegal[229] DTaP 6,881 n/a 0 0 0.29

DTP 6,595 n/a 0 1.2 0.39

HHE, hypotonic-hyporesponsive episode; n/a, data not available.

* Note that duration of surveillance or definitions of adverse reactions may have varied from trial to trial. Thus, comparisons within trials are more valid than comparisons across trials.

† Fever ≥40.5°C for Erlangen; for Munich, rate ofexcept:

‡ Crying persisting ≥3 hrs, except that duration not specified for Erlangen and Göteborg.

§ Within 48 hrs of vaccination.

Infanrix (GlaxoSmithKline)

In the Italian trial, adverse events were significantly more common among recipients of DTP than DTaP or DT. Temperature of 40.5°C or greater was seen in 6.8% of recipients of DTP, 0.8% of recipients of Infanrix, 1.1% of recipients of Triacelluvax and 1.3% of recipients of DT; crying 3 or more hours in 11.5%, 1.9%, 1.3%, and 0%, respectively; and HHE in 1.7%, 0.2%, 0%, and 1.3%, respectively.[448] Seizures within 48 hours of vaccination occurred in one Infanrix recipient and in three DTP recipients.[230]

Triavax (Sanofi Pasteur, France)

In the Senegal efficacy study, Triavax and Sanofi Pasteur's French whole-cell vaccine were each given to approximately 2,200 children. Persistent crying was significantly more common among whole-cell recipients (eight vs. zero episodes). Two subjects in each group experienced febrile seizures within 48 hours of vaccine administration. No episodes of HHE or anaphylactic reactions were seen. In the pilot

73 study preceding this trial, fever, crying, and local reactions were significantly more common with whole- cell than acellular vaccine.[290]

Daptacel (Tripacel) (Sanofi Pasteur Ltd, Canada)

Of the 2,552 children given the classical (CLL-4F2) formulation of Tripacel in Stockholm 1992, one (0.04%) had HHE and another was withdrawn as a result of pronounced local reactions.[229] There were seven episodes of convulsions, but none occurred within 48 hours of vaccination, making a causal association unlikely. Of 17,686 children given the hybrid (HCPDT) formulation of Tripacel in Stockholm 1993, 0.04% had fever of 40°C or greater and 0.02% had convulsions within 48 hours of vaccine administration. [408] Minor local and systemic reactions were significantly less common with HCPDT than with whole-cell vaccine. The investigators made a special effort to detect HHE in Stockholm 1993, and thus higher HHE rates were recorded for vaccines evaluated in that study than for the same, or similar, vaccines evaluated in other studies. HHE rates were, for Tripacel, 0.47 per 1,000 in Stockholm 1993 (hybrid formulation) versus 0.13 per 1,000 in Stockholm 1992 (classical formulation); and for Triacelluvax, 0.26 per 1,000 in Stockholm 1993 versus 0.07 per 1,000 in Italy 1992.

Tripedia (Sanofi Pasteur, USA)

Of 12,514 children given Tripedia in the Munich trial, 2.2% experienced the following adverse events related to vaccination: fever, 0.9%; local reactions, 0.4%; unusual crying, 0.3%; irritability, 0.3%; somnolence, 0.2%; crying more than 3 hours, 0.04%; HHE, 0.02%; and febrile seizure, 0.01%.[218,286,408] Ten children given Tripedia had culture-confirmed invasive bacterial disease, but the rate of disease was not significantly higher than that seen in the control group.

Severe adverse events: national surveillance data

The claims paid by the Japanese Vaccine Compensation System provide a comparison of severe neurologic reactions and deaths with whole-cell versus acellular vaccine and with immunization beginning at 3 months versus 2 years.[267,269,449] As shown in Table 21-16, changing the age of administration of whole-cell vaccine from 3 months to 2 years was associated with a dramatic reduction in compensable adverse neurologic events and deaths; a further reduction occurred with the change from whole-cell to acellular vaccine. The data strongly suggest that this low rate of serious adverse events was maintained after the initiation of immunization with acellular vaccine at the age of 3 months in 1989. Severe neurologic events and deaths both were reduced more than eightfold during 13 years of acellular vaccine use, as compared with the preceding 11 years of whole-cell vaccine use (see Table 21- 16).

Table 21-16 -- Japanese Vaccine Injury Compensation System Claims, 1970–1993

74 Number of Claims Claims per 106 Doses

Reporting Vaccines InDoses, Vaccination Age, Neurologic Total Neurologic Total Period Use Millions 1st Dose Events[*] Deaths[†] Events[‡] Deaths[‡]

Jan 1970–JanWhole Cell 3 months 86 37 1975

Feb 1975– Whole Cell 2 years 23 3 Aug 1981

Sep 1981– Acellular 2 years 11 2 Dec 1984

1970–1980, Whole Cell 44.9 3 mos, 1970–75; 2 18.5 7.4 Overall yrs, 1975–80

1981–1993, Acellular 62.6 2 yrs, 1981-1988; 3 2.4 0.9 Overall mos thereafter

* Claims approved for neurological illnesses within 7 days after DTP immunization. Data from Kimura M, Kuno-Sakai H. Current epidemiology of pertussis in Japan. Pediatr Infect Dis J 1990;9:705–709.

† Number of deaths included among claims paid. Data from Noble GR, Bernier RH, Esber EC et al. Acellular and whole-cell pertussis vaccine in Japan: Report of a visit by U.S. scientists. JAMA 257:1351– 1356, 1987.

‡ Rate per 10 million doses of cases applied to the compensation system. Data from Kuno-Sakai H, Kimura M. Epidemiology of pertussis and use of acellular pertussis vaccines in Japan. Dev Biol Stand 89:331– 332, 1997.

The Alberta, Canada, public health system provided all immunizations and conducted uniform surveillance for postimmunization adverse events during the years preceding and following the transition in Canada from whole-cell to acellular pertussis vaccines. Prior to July 1, 1997, a pentavalent DTP-IPV-Hib combination vaccine was used in the province; beginning July 1, a DTaP-IPV-Hib combination was used (this combination, Pentacel, is based on the HCPDT version of Tripacel that was studied in Stockholm 1993). The switch to the acellular combination was associated with an 89% reduction in fever greater than 40°C, an 82% reduction in unusual cry, and a 74% reduction in HHE. [450] These results were confirmed by Scheifele et al., who evaluated emergency room visits and hospitalizations at tertiary-care pediatric centers across Canada and found an 86% decline in febrile seizures and a 75% decline in HHE coincident with the transition from whole-cell to acellular-based combination vaccines in Canada.[451]

Similar data, albeit less dramatic, are available from the U.S. Vaccine Adverse Event Reporting System (VAERS), maintained by the CDC and the FDA.[452] From 1991 to 1993, rates of reported adverse events

75 after the fourth and fifth doses in the pertussis immunization series were significantly lower for DTaP than DTP. These events included fever (1.9 vs. 7.5 events per 100,000 vaccinations), seizures (0.5 vs. 1.7), and hospitalization (0.2 vs. 0.9), for a total of 2.9 versus 9.8 cases per 100,000 vaccinations for DTaP and DTP, respectively.[453] There were three reports of encephalopathy after DTP, but none after DTaP. A follow-up report, covering the period between January 1, 1995 (when whole-cell vaccine was in exclusive use), and June 30, 1998 (when acellular vaccine was in predominant use), revealed steadily declining annual numbers of VAERS reports involving immunization against pertussis, from 2,071 in 1995 to 491 in the first half of 1998.[454]

Results of booster doses given to children previously primed with acellular vaccine

A continuation study of the MAPT evaluated the safety and immunogenicity of a fourth dose of acellular vaccine given at 15–20 months to children who had been primed with either acellular or whole-cell vaccine at 2, 4, and 6 months of age.[455] For children who received four consecutive doses of an acellular vaccine, fever and injection site redness, swelling, and pain were seen more frequently with the fourth dose than with the primary series. Of children given a booster with acellular vaccine, those who had been primed with acellular vaccine had local redness and swelling significantly more frequently than did those who had been primed with whole-cell vaccine. However, children who received four consecutive doses of whole-cell vaccine had significantly higher rates of irritability, redness, swelling, and pain after the booster than did either of the groups that were given a fourth dose of acellular vaccine. None of 1,293 evaluated children experienced seizures, HHEs, or fever greater than 105°F. Also of note, several cases of entire limb swelling were observed after administration of the fourth dose of acellular vaccine to children previously primed with DTaP.

A report from Germany of entire limb swelling occurring after the fourth dose of one three-component DTaP had appeared in 1997. Among children from whom adverse reactions were specifically solicited, the rate of entire thigh swelling was 2.4%, whereas it was reported to occur in only 0.5% of those not specifically followed for reactions.[456] With this report in mind, Rennels et al. evaluated the cases of entire limb swelling after the fourth dose of acellular pertussis vaccine in MAPT.[457] Although extensive swelling reactions had not been anticipated in MAPT and had not been prospectively studied, parents in MAPT had been provided with diary cards that contained a section for them to report other reactions of concern. Parents of 20 (2%) of the 1,015 children who had received the same DTaP vaccine throughout the primary and booster series described swelling of the entire thigh after the fourth dose. In contrast, none of the 246 children primed with DTP and boosted with DTaP were reported to have entire thigh swelling. Differences in rates between the whole-cell and acellular-primed groups were significant (P=0.02). An interesting observation was that 40% of these children with whole-limb swelling were judged by their parents to have experienced no pain and 40% were judged not to have erythema, in spite of the extensive swelling reactions. The only significant association between rates of entire thigh swelling following dose 4 and the composition of the associated vaccine was with the quantity of diphtheria toxoid (P=0.02). Antibody levels to pertussis toxoid, diphtheria toxoid, and tetanus toxoid were evaluated for subjects with extensive swelling and three controls per case in an attempt to determine whether the swelling might be due to an Arthus reaction. No difference was noted in the comparative distribution of pre- and postvaccination antibody titers between cases and controls, but

76 sample sizes were small. In contrast, a large study of children given a fifth dose of Tripedia found that higher prevaccination antibody titers were associated with a higher frequency of large local reactions. [458] Thus, there is some evidence that high IgG antibody levels prior to booster vaccination might play a role in the large limb swelling and may be related to excessive antigen content.

Children enrolled in MAPT were also studied after the fifth dose of DTaP.[459] Given the 5-year interval between initial enrollment and the fifth dose, many children were not located for enrollment in the study. None of 121 children given five doses of the same DTaP, versus four (2.7%) of 146 children receiving a mixed DTaP series, were reported to have experienced swelling of the whole upper arm following the fifth dose (P=0.13). For children with swelling after the fifth dose, the onset of swelling was noted by parents on days 1 and 2 postvaccination and generally resolved by day 4, with no sequelae.

Rennels and colleagues reanalyzed data from the fourth-dose and fifth-dose MAPT studies and found no consistent relation between the quantity of aluminum in various DTaP vaccines and their rates of extensive swelling.[460] Further review of the literature regarding extensive swelling reactions reveals other sporadic reports in early studies of acellular pertussis vaccines in Japan[460,461] and Sweden.[462] The proposed explanation at that time was that immunizations had been given by the deep subcutaneous and not the intramuscular route. This observation was supported by the report that shorter needle length was associated with increased local reactions.[463] However, in the MAPT studies, the extensive swelling was seen with nine of the 12 DTaP vaccines (containing from one to five pertussis antigens), which were given intramuscularly by experienced vaccine study nurses.[457] The pathophysiology of the large local reactions seen after booster injections of DTaP vaccine probably is multifactorial and may represent a cumulative increased response to several component antigens. Both whole-cell pertussis vaccine and tetanus toxoid have been documented to cause large local reactions. Previous studies have shown an association between severe local reactions and immunoglobulin E antibody levels to the toxoid vaccines, which are enhanced by aluminum absorption.[464–466] CMI may play a role in sensitization of certain individuals to repeated doses of toxoid vaccines, a possibility that needs further assessment. [378,467] In addition, there are data indicating that children with large erythematous reactions after DTaP vaccines more commonly react to skin test patches containing DT or acellular pertussis antigens.[468]

In a randomized, blinded study of DTaP-IPV and Tdap vaccines (similarly formulated except for the concentrations of PT, diphtheria toxoid and IPV) among children 4–6 years of age, Scheifele and colleagues found that rates of large injection site reactions and of pain were lower by half to two thirds in the group receiving the Tdap vaccine. Children with large reactions were more likely to have relatively elevated prevaccination antibody levels to PT, PRN, or diphtheria toxin.[469] Similar findings were reported by Knuf et al. in children receiving booster doses of DTaP during the second year of life where local reactions were reduced after vaccines containing lesser quantities of antigens.[470]

Summary of adverse events

Almost every study has found minor local and systemic adverse reactions to be less common with acellular than whole-cell vaccine. Although HHEs and seizures are seen after acellular vaccine, they occur less frequently than with whole-cell vaccine.

77 Rates of rare adverse effects cannot be determined reliably even with large efficacy trials, and they require postmarketing surveillance for their determination. Of course, adverse events temporally but not causally associated with vaccination will continue to occur at their background rates regardless of the vaccine used. Among children primed and boosted with acellular vaccine, reaction rates increase successively with each booster dose but remain lower than seen among children primed and boosted with whole-cell vaccine.

Vaccination of adolescents and adults

Numerous acellular pertussis vaccines have been evaluated in adults.[318,471–473,474–476] All appear highly immunogenic, with few adverse reactions. As noted previously, Tdap vaccines have been licensed in various jurisdictions for immunization of adolescents and adults under the brand names Adacel, Boostrix, Covaxis, and (combined with IPV) Repevax.

Several groups of experts[242,477] have encouraged development and use of acellular pertussis vaccines for adolescents and adults. The International Consensus Group on Pertussis Immunisation[242] and the Global Pertussis Initiative[477] both have recommended universal adolescent booster vaccination combined with targeted immunization of those adults most likely to have contact with babies, including parents and other close family members, healthcare workers, and day care workers; universal immunization of young adults; and routine use of Tdap rather than Td for all adult booster immunizations. In 2005, the Global Pertussis Initiative published a series of papers offering detailed evaluations and region-specific recommendations for further control of pertussis, particularly including adolescent-adult immunization. [478–486]

An additional strategy that has been discussed is the use of Tdap, rather than DTaP, at the 4–6-year booster, to reduce the adverse reactions associated with the current approach. In that regard, it is of interest that the European licensing authority has just modified the marketing authorization of Boostrix to include children age 4 and above; presumably, similar approval will be sought for other markets and other Tdap vaccines (e.g., Adacel).

Adverse reactions in adolescents and adults

A National Institutes of Health (NIH)-sponsored multicenter trial evaluated the immunogenicity and reactogenicity in adults of varying strengths of five acellular pertussis vaccines (variants of Certiva, Triacelluvax, Infanrix, ACEL-IMUNE, and a PT-FHA vaccine supplied by the Massachusetts Public Health Biologic Laboratories).[471,476] All vaccine dose strengths were well tolerated, although dose-related increases in the rates of injection-site symptoms and the duration of injection-site discomfort were seen in some subjects. Late-onset or biphasic reactions, generally minor, were noted in this study, as they had been in some prior studies. The frequency of these late reactions seemed to be greater for the higher- strength doses and for vaccines with more antigens.

Large-scale clinical trials of the Tdap vaccines demonstrated generally similar reaction profiles for them as for Td vaccines; in other words, the addition of purified acellular pertussis components to Td adds essentially nothing to the adverse reaction profile. Biphasic or late reactions generally were not seen,

78 and large local reactions were rare or not seen.[487–489] However, it should be noted that these studies were conducted in adolescents and adults who had been primed with whole-cell vaccine and who had received zero, one, or at most two prior injections of acellular vaccine. Recently the safety of a booster dose of a reduced-antigen-content tetanus-diphtheria-acellular pertussis (Tdap) vaccine was evaluated in adolescents previously vaccinated with five doses of acellular pertussis-containing vaccine. Pain (63.6%), redness (51.7%), and swelling (41.4%) were the most frequently reported AEs after the sixth dose than after earlier doses. In contrast, large injection site swelling (swelling > 100 mm, arm circumference increase > 50 mm or dif-fuse swelling interfering with daily activities) occurred in only three adolescents and resolved without sequelae. Additional studies to evaluate the reaction profiles after repeated doses of Tdap are in progress.[489a]

The question of the minimum safe interval between prior diphtheria, tetanus, or pertussis vaccination and Tdap was addressed in a large-scale study conducted in Prince Edward Island, Canada.[490] All consenting provincial school-children (n=7,156) in grades 3–12 (except grade 10, who received the vaccine the prior year) were given Tdap and reactions were compared by time since prior vaccine (range, 18 months to >10 years, the latter serving as the comparison group). No variation in adverse reactions was found based on time since last Td; a slight increase in redness and swelling was found for those who had previously received DTaP, as compared to those who had only previously received whole-cell DTP.

Immunogenicity in adolescents and adults

All the studies just mentioned demonstrated excellent immunogenicity of the acellular vaccines in adults, even with doses substantially lower than the standard pediatric dose. In a study of the Lederle- Takeda vaccine, antibody responses to PT, FHA, fimbrial proteins, and PRN, even at the lowest dose, exceeded those seen in infants after complete primary immunization with the same vaccine.[473] No interference was noted with diphtheria or tetanus antibody responses in any of the groups. Similar findings were reported with the same vaccine when studied in German adults.[475] In the NIH dose- ranging study, dose-related increases in serum antibody levels against known vaccine antigens were seen in all vaccine groups.[471,476] For several vaccines, significant antibody responses were seen against antigens not known to be present in the vaccines, suggesting that the vaccines contained trace quantities of these antigens and were stimulating an anamnestic response in these adults, who had been immunized in childhood with whole-cell vaccine.

Efficacy in adolescents and adults

An NIH-sponsored study, the APERT trial, evaluated the efficacy of an acellular pertussis vaccine in adolescents and adults.[491] This prospective trial, conducted at eight centers across the United States, randomized 2,781 healthy subjects ages 15–65 years to receive either an acellular pertussis vaccine (Boostrix minus the Td components) or hepatitis A vaccine. For 2 years, subjects were actively followed for pertussis illness with phone calls every 2 weeks (a total of more than 58,000 person-months of surveillance). Serum specimens were obtained at routine intervals; for any cough illness lasting 5 days or longer, serum specimens and nasopharyngeal aspirates for culture and PCR were obtained.

79 The acellular pertussis vaccine was well tolerated, with fewer than 5% of subjects reporting minor local or systemic adverse reactions. The study and control groups did not differ in the rate of severe adverse events, none of which were considered vaccine related. Local reactions were detected more commonly in females than males.

Cough illnesses lasting 5 or more days were reasonably common (more than one per every 2 person- years) and were seen equally in both study groups. There were four well-documented pertussis infections per 1,000 patient-years of follow-up; the incidence was highest in subjects 15–30 years of age and in those with cough illnesses of longest duration. A variety of case definitions were evaluated based on the strength of the laboratory evidence (positive culture, PCR, or rise in pertussis-specific antibodies in paired acute-convalescent specimens). There was a significantly lower incidence of pertussis in acellular pertussis vaccinees than controls; the point estimate of vaccine efficacy was 92% (95% CI, 32– 99%). The rate of pertussis seen in the APERT trial is quite consistent with rates identified in other studies of adult pertussis (see Epidemiology, above) and suggests that there are between 1 and 1.5 million pertussis illnesses per year in the United States among adolescents and adults.[171]

Many authorities have thought that licensure of acellular pertussis vaccine for adult use was warranted even without specific efficacy data, based on immunogenicity and safety data in adults coupled with efficacy and other data from studies conducted in children. Certainly, now that efficacy of an adult- formulation acellular vaccine has been demonstrated, routine use of these vaccines to boost immunity in adolescents and adults has been recommended. Healthcare workers, child care workers and adolescents and adults in households containing children (particularly newborns) are among the high- priority target groups for immunization.[492a,b]

Indications for vaccine

With licensure of the combination DTaP vaccine for primary vaccination of infants, recommendations for the use of pertussis vaccine in the United States have been modified extensively. Both the ACIP and the Red Book Committee have recommended that the acellular vaccine be preferred for all doses in the vaccination schedule, although DTP remains an acceptable alternative for any of the five doses (albeit no longer commercially available in the United States).

Immunization of infants and children

In the United States, unless specifically contraindicated (see later), every infant should receive pertussis vaccine at ages 2, 4, and 6 months and 12–18 months; a booster is indicated at 4–6 years of age. The timing of infant vaccination is determined by birth age, without regard to prematurity.[186,317]Children whose vaccination series has been interrupted need not have prior doses repeated but should have their series resumed at the earliest opportunity.

At present, no formulation of DTaP combined with Hib vaccine is licensed in the United States for primary immunization of infants; one such formulation (TriHIBit) is approved for the fourth (booster) dose of the DTaP series (the third or fourth dose of the Hib series, depending on the prior Hib vaccine[s] used). A combination vaccine containing DTaP, IPV, and HBV (Pediarix) is available in the United States

80 for use in infants, and a license application has been submitted for a combination of DTaP, IPV, and Hib (Pentacel). Many such combinations already are licensed elsewhere (see Chapter 36).

Immunization of adolescents and adults

Following the recent licensure of two Tdap vaccines in the U.S. (Boostrix and Adacel), the ACIP and other advisory groups have made a series of recommendations for use of the vaccine in the US. Adolescents between the ages of 11–18 years are recommended to receive a single dose of Tdap instead of Td for booster immunization against tetanus, diphtheria, and pertussis if they have completed the recommended childhood DTP/DTaP series and have not received Td or Tdap vaccines. The preferred age of Tdap immunization is 11–12 years of age. Adolescents aged 11–18 years who have received Td, but not Tdap, are encouraged to receive a single dose of Tdap if they have completed the recommended childhood DTP/DTaP series. To reduce the risk of local and systemic adverse reactions, an interval of at least 5 years between the Td and Tdap vaccines is encouraged, however an interval of less than that can be used if the risk of pertussis outweighs the risk for adverse reactions. Vaccine providers were also encouraged to administer Tdap and tetravalent meninogococcal conjugate vaccine to these adolescents at the same visit if both were indicated and available.

Adolescents who received DT or Td vaccination instead of one or more doses of pediatric DTP/DTaP in the childhood series should receive a single dose of Tdap if they have completed the recommended series for diphtheria and tetanus and have no contraindications to the pertussis components. If they have never been vaccinated against tetanus, diphtheria, or pertussis, they should receive a series of three tetanus- and diphtheria-containing vaccines. The preferred schedule is a single dose of Tdap, followed by a dose of Td 1 month or more after the Tdap, and a second dose of Td 6–12 months after the earlier dose. However, Tdap can be substituted for any one of the Td doses in the series.

On October 26, 2005 the ACIP recommended routine use of a single dose of Tdap for adults 19–64 years of age to replace the next booster dose of Td. Since Boostrix is only licensed for individuals 10–18 years of age, Adacel must be used in the older populations. Tdap is not licensed for individuals over 65 years and thus no recommendations exist for its use in that age group. The ACIP also recommended Tdap for adults who have close contact with infants <12 months of age and suggested that it be given at least 1 month before beginning close contact with the infant. They also recommended that women should receive a dose of Tdap in the immediate post-partum period if they have previously not received Tdap. On February 22, 2006, the ACIP also recommended Tdap for healthcare personnel. They suggested that priority be given to healthcare workers with direct contact with infants <12 months of age but others should be immunized with Tdap as vaccine becomes available. An interval of 5 years since prior T- or D- containing vaccine is recommended, but in light of the evidence regarding safety when administered at shorter intervals, no minimum intervals are required if the clinical situation (e.g., a pertussis outbreak) warrants such vaccination.

Pregnancy is not a contraindication to Tdap or Td vaccination, but concern has been raised that high levels of transplacentally derived maternal antibody might inhibit the subsequent immune response to infants vaccinated with DTaP. Studies are planned to investigate this possibility.[493,494]

81 In Canada, where Adacel has been licensed for several years, the Canadian National Advisory Committee on Immunization has recently recommended that Tdap should be used to replace the adolescent booster of Td, and that unimmunized children older than 6 and immigrants of uncertain immunization status should receive two doses of Tdap with a 4-week interval, followed by a third dose at 12 months after the first.[495] Similarly, in 2002, the Austrian Standing Commission on Immunization Plan noted the increasing incidence of pertussis in adolescents and adults and called for routine use of Tdap (Tdap-IPV, when available) at 7 years, 14–15 years, and every 10 years thereafter.

Use of vaccine in outbreaks – children

Immunization initiated after a pertussis exposure does not protect from that exposure; in an outbreak, however, exposure opportunities are ongoing and the existence of an outbreak should reinvigorate efforts to properly immunize those children who have not completed a full vaccination schedule. An accelerated infant vaccination schedule (e.g., 4, 8, and 12 weeks of age) may be indicated.[203] There is no evidence that supplemental doses of pertussis vaccine are required during an outbreak for the protection of normal children who have received pertussis immunization in accord with the recommended schedule. Supplemental immunization of children who have immunologic or cardiopulmonary compromise may be considered if the benefits of vaccination are believed to outweigh the risks of adverse reactions.

Use of vaccine in outbreaks – adolescents and adults

Even prior to the availability of the Tdap vaccines, the reduced adverse reaction profile of acellular vaccines had already stimulated use, or recommendations for use, of pediatric formulations among healthcare workers during hospital-based or community outbreaks.[496,497] Now that Tdap vaccines are available, they clearly are preferred for this purpose. The ACIP recommendations anticipate this usage by setting no minimum interval since last vaccination when the risk of pertussis disease warrants use of Tdap. The efficacy of such immunization is as yet unproven; clearly, however, vaccination is most likely to be beneficial if it is begun as early as possible in the epidemic.

Precautions and contraindications

Normal infants and children

Older recommendations regarding contraindications and precautions for pertussis vaccination reflected concerns stemming from the whole-cell pertussis vaccine and are not supported by recent data with acellular vaccines. At present, there are but two true contraindications to the use of pertussis vaccine: anaphylaxis or encephalopathy following administration of a vaccine containing a pertussis component. [186,317]

An anaphylactic reaction occurring immediately after administration of DTaP or whole-cell DTP is a contraindication to further vaccination with separate diphtheria, tetanus, or pertussis (acellular or whole-cell) components, absent proof as to which of these three components was responsible. Given the importance of tetanus vaccination, referral to an allergist for tetanus toxoid desensitization may be

82 indicated. Acute encephalopathy occurring within 7 days after administration of DTP or DTaP, not attributable to another identifiable cause, is a contraindication to further pertussis immunization. DT vaccine should be administered for the remaining doses in the vaccination schedule, although it may be appropriate to delay vaccination until the patient's neurologic status clears.[186,317]

The following are now considered precautions, not contraindications, to pertussis vaccine: temperature 40.5°C (105°F) or greater within 48 hours of pertussis vaccination and not due to another identified cause; collapse or shock-like state (HHE) within 48 hours; persistent, inconsolable crying lasting 3 or more hours within 48 hours after vaccination; and convulsions occurring within 3 days, with or without fever. Decisions regarding the further administration of pertussis vaccine should be guided by an individualized evaluation of benefits and risks.[186,317] The risks are likely to be substantially lower if acellular, rather than whole-cell, pertussis vaccine is used.

A family history of seizures, of adverse reactions to vaccine, or of allergy to vaccine is not a contraindication to the receipt of DTP or DTaP. Administration of pertussis vaccine should be deferred briefly for children with moderate or severe acute illnesses, with or without fever; they may be vaccinated as soon as they recover. Children who are immunocompromised or are receiving immunosuppressive therapy may be vaccinated with DTP or DTaP. If immunosuppressive therapy will be discontinued soon, deferral of vaccination until 1 month after therapy may permit better immune responses.

Children with neurologic disorders

As is discussed above under Adverse Events with Whole-Cell Vaccines, pertussis vaccine may precipitate febrile convulsions and may unmask neurologic disorders that would soon have become evident anyway, but it does not appear to cause or worsen chronic neurologic disorders. Because children with neurologic impairments are as needful—indeed, perhaps more needful—of protection from pertussis disease, any decision to decline pertussis vaccination should reflect a careful consideration of risks and benefits, particularly in light of the increasing incidence of pertussis.[186,317] It may be appropriate to delay pertussis vaccination of infants with neurologic disorders until their status is clarified, but again careful consideration is required. The highest risk of pertussis is in the first 6 months of life, whereas the risk of febrile convulsions is higher thereafter; both factors therefore argue for adherence to the standard primary immunization schedule.

Children with prior convulsions should probably have pertussis vaccine deferred until the cause of the convulsions is assessed and any necessary treatment is established. Febrile seizures unrelated to pertussis vaccine are not a contraindication to further vaccination, nor is a family history of seizures. [317] Administration of acetaminophen at a dose of 15 mg/kg should also be considered at the time of vaccination and every 4 hours for the ensuing 24 hours to reduce the risk of fever associated with vaccination.[317]

False contraindications to dtap

83 A number of situations have been considered incorrectly to be contraindications, and deferral of pertussis vaccination on these bases is inappropriate: redness, swelling, or pain at the injection site; temperature less than 40.5°C (105°F); mild acute illness, even involving diarrhea or low-grade fever; current antibiotic therapy; recent exposure to an infectious disease; prematurity; personal or family history of allergies; and family history of SIDS, convulsions, or adverse event after pertussis vaccination. [317] Prior pertussis infection is not a contraindication to vaccination; although a previously infected child may not require vaccination for immunity, proceeding with vaccination obviates the risk that the prior illness was not in fact pertussis.

Adolescents and adults

For adolescents and adults, the only contraindications to Tdap vaccine are a history of serious allergic reaction to a component of the vaccine and a history of encephalopathy not attributable to another identifiable cause within 7 days following pertussis vaccination. Precautions include a history of a vaccine-related Arthus reaction, Guillaine–Barré syndrome, or progressive neurological reaction; in such cases, individualized consideration should be given to risks and benefits.

Other reactions after pediatric vaccination, including high fever, syncope, seizure, HHE, and large local reaction, are not contraindications or precautions, nor a prior diagnosis of pertussis.

Public health considerations

Disease control strategies

There is but one disease control strategy for pertussis: vaccination. But with which vaccine? Numerous whole-cell and acellular pertussis vaccines have been evaluated in efficacy trials. Which ones should be used?

In North America and Europe, acellular vaccines are widely used and have largely or entirely replaced the whole-cell vaccines. National surveillance indicates excellent control of pertussis in the vaccinated populations; increases in incidence are seen only in populations not receiving vaccine. In most countries, multivalent combination vaccines are used (see Chapter 36).

Outside North America and Europe, many countries use the acellular vaccines (usually as combinations) in the private market but few countries have implanted them in their national vaccination programs. Such countries will have to apply their own relative weights when evaluating the comparative cost, efficacy, and adverse effects of the acellular and whole-cell vaccines.[498] Many countries may decide that their present whole-cell vaccine offers unsurpassed efficacy at low cost; if the vaccine is well accepted by the public, no change would be indicated. However, with the increasing availability of combination vaccines, these decisions are likely to become even more complex (see Chapter 36). For example, if the national program desires to provide IPV, Hib, or HB vaccine, the country may find that the cost of a DTaP-based combination is little more than the stand alone IPV, Hib, and HB vaccines.

Eradication or elimination

84 Humans are the only reservoir for pertussis, and chronic carriage is not known to occur. In principle, then, pertussis can be eradicated. Acellular vaccines are suitable for use among all age groups, but it remains to be seen whether their widespread use can interrupt transmission of pertussis within a region. Global eradication, although perhaps possible, clearly must be many years away.

References

1. Holmes WH: Bacillary and rickettsial infections, acute and chronic; a text-book, black death to white plague, New York: The Macmillan company; 1940:395-398.

2. Hardy A: Whooping Cough. In: Kiple KF, ed. Paper presented at: The Cambridge World History of Human Disease, New York: Cambridge University Press; 1993:1094-1096.

3. Bordet J, Gengou O: Le microbe de la coqueluche. Ann Inst Pasteur 1906; 20:731-741.

4. Cherry J, Brunnel P, Golden G: Report of the Task Force on Pertussis and Pertussis Immunization, 1988. Pediatrics 1988; 81(suppl):933-984.

5. Pertussis vaccination use of acellular pertussis vaccines among infants and young children. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 1997; 46(RR-7):1-25.

6. Pertussis – United States, 1997–2000. MMWR Morb Mortal Wkly Rep 2002; 51(4):73-76.

7. Broder KR, Cortese MM, Iskander JK, et al: Preventing tetanus, diphtheria, and pertussis among adolescents: use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccines recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2006; 55(RR-3):1-34.

7a. Preventing Tetanus Diphtheria, and Pertussis Among Adults : Use of to diagnose pertussis (66). Use of PCR tests with low specificity can result in unnecessary investigation and treatment of persons with false-positive PCR test.

www.cdc.gov/mmwr/preview/mmwrhtml/rr5517a1.htm?s_cid=rr5517a1_e

7b. Cortese MM, Baughman AL, Brown K, Srivastava P: A “new age” in pertussis prevention new opportunities through adult vaccination. Am J Prev Med 2007 Mar; 32(3):177-185.

8. Pertussis Reported Cases (interactive online data table). Geneva: World Health Organization. Online. Accessed August

8, 2002 Available at: www.nt.who.int/vaccines/globalsummary/timeseries/TSincidencePer.htm

9. Zackrisson G, Taranger J, Trollfors B: History of whooping cough in nonvaccinated Swedish children, related to serum antibodies to pertussis toxin and filamentous hemagglutinin. J Pediatr 1990; 116(2):190-194.

10. Heininger U, Klich K, Stehr K, Cherry JD: Clinical findings in Bordetella pertussis infections: results of a prospective multicenter surveillance study. Pediatrics 1997; 100(6):E10.

11. Lapin JH: Whooping Cough, Springfield, Ill, Baltimore, Md., C.C. Thomas, 1943.

12. Halasa NB, Barr FE, Johnson JE, Edwards KM: Fatal pulmonary hypertension associated with pertussis in infants: does extracorporeal membrane oxygenation have a role. Pediatrics 2003; 112(6 Pt 1):1274-1278.

13. Williams GD, Numa A, Sokol J, et al: ECLS in pertussis: does it have a role. Intensive Care Med 1998; 24(10):1089- 1092.

85 14. Wortis N, Strebel PM, Wharton M, et al: Pertussis deaths: report of 23 cases in the United States, 1992 and 1993. Pediatrics 1996; 97(5):607-612.

15. Sreenan CD, Osiovich H: Neonatal pertussis requiring extracorporeal membrane oxygenation. Pediatr Surg Int 2001; 17(2–3):201-203.

16. Chan L: Cough and respiratory distress in a two-month-old infant. Pediatr Infect Dis J 1997; 16(6):631-632, 634–635.

17. Gillis J, Grattan-Smith T, Kilham H: Artificial ventilation in severe pertussis. Arch Dis Child 1988; 63(4):364-367.

18. Goulin GD, Kaya KM, Bradley JS: Severe pulmonary hypertension associated with shock and death in infants infected with Bordetella pertussis. Crit Care Med 1993; 21(11):1791-1794.

19. Pierce C, Klein N, Peters M: Is leukocytosis a predictor of mortality in severe pertussis infection. Intensive Care Med 2000; 26(10):1512-1514.

20. Plott K, Pascual F: Pertussis deaths—United States 2000. MMWR 2002; 51:616-618.

21. Johnston ID, Bland JM, Ingram D, et al: Effect of whooping cough in infancy on subsequent lung function and bronchial reactivity. Am Rev Respir Dis 1986; 134(2):270-275.

22. Grant CC, McKay EJ, Simpson A, Buckley D: Pertussis encephalopathy with high cerebrospinal fluid antibody titers to pertussis toxin and filamentous hemagglutinin. Pediatrics 1998; 102(4 Pt 1):986-990.

23. Mikelova LK, Halperin SA, Scheifele D, et al: Predictors of death in infants hospitalized with pertussis: a case-control study of 16 pertussis deaths in Canada. J Pediatr 2003; 143(5):576-581.

24. Litvak A, Gibel H, Rosenthal S: Cerebral complications in pertussis. J Pediatr 1948; 32:357-379.

25. Great Britain : Committee on Safety of Medicines., Great Britain. Joint Committee on Vaccination and Immunisation., Great Britain. Dept. of Health and Social Security. Whooping cough: reports from the Committee on Safety of Medicines and the Joint Committee on Vaccination and Immunisation, London: H.M.S.O.; 1981:184.xiii

26. Zellweger H: Pertussis encephalopathy. Arch Pediatr 1959; 76:381-386.

27. Nelson JD: The changing epidemiology of pertussis in young infants. The role of adults as reservoirs of infection. Am J Dis Child 1978; 132(4):371-373.

28. De Serres G, Shadmani R, Duval B, et al: Morbidity of pertussis in adolescents and adults. J Infect Dis 2000; 182(1):174-179.

29. Bisgard KM, Pascual FB, Ehresmann KR, et al: Infant pertussis: who was the source. Pediatr Infect Dis J 2004; 23(11):985-989.

29a. Wendelboe AM, Njamkepo E, Bourillon A, et al: Infant Pertussis Study Group. Transmission of Bordetella pertussis to young infants. Pediatr Infect Dis J 2007 Apr; 26(4):293-299.

30. Senzilet LD, Halperin SA, Spika JS, et al: Pertussis is a frequent cause of prolonged cough illness in adults and adolescents. Clin Infect Dis 2001; 32(12):1691-1697.

31. Schmitt-Grohe S, Cherry JD, Heininger U, et al: Pertussis in German adults. Clin Infect Dis 1995; 21(4):860-866.

32. Postels-Multani S, Schmitt HJ, Wirsing von Konig CH, et al: Symptoms and complications of pertussis in adults. Infection 1995; 23(3):139-142.

33. Long SS, Lischner HW, Deforest A, Clark JL: Serologic evidence of subclinical pertussis in immunized children. Pediatr Infect Dis J 1990; 9(10):700-705.

34. Cromer BA, Goydos J, Hackell J, et al: Unrecognized pertussis infection in adolescents. Am J Dis Child 1993; 147(5):575-577.

86 35. Long SS, Welkon CJ, Clark JL: Widespread silent transmission of pertussis in families: antibody correlates of infection and symptomatology. J Infect Dis 1990; 161(3):480-486.

36. Eidlitz-Markus T, Zeharia A: Bordetella pertussis as a trigger of migraine without aura. Pediatr Neurol 2005; 33(4):283- 284.

37. Skowronski DM, Buxton JA, Hestrin M, et al: Carotid artery dissection as a possible severe complication of pertussis in an adult: clinical case report and review. Clin Infect Dis 2003; 36(1):e1-e4.

38. Jenkins P, Clarke SW: Cough syncope: a complication of adult whooping cough. Br J Dis Chest 1981; 75(3):311-313.

39. Halperin SA, Marrie TJ: Pertussis encephalopathy in an adult: case report and review. Rev Infect Dis 1991; 13(6):1043- 1047.

40. MacLean DW: Adults with pertussis. J R Coll Gen Pract 1982; 32(238):298-300.

41. Fatal case of unsuspected pertussis diagnosed from a blood culture—Minnesota, 2003. MMWR Morb Mortal Wkly Rep 2004; 53(6):131-132.

42. Manclark CR, Cowell JL: Pertussis. In: Germanier R, ed. Bacterial vaccines, Orlando: Academic Press; 1984:69-106.

43. Kloos W, Mohapatra N, Dobrogosz W: Deoxyribonucleotide sequence relationship among Bordetella species. Int J Syst Bacteriol 1981; 31:173-176.

44. Bjornstad ON, Harvill ET: Evolution and emergence of Bordetella in humans. Trends Microbiol 2005; 13(8):355-359.

45. Arico B, Rappuoli R: Bordetella parapertussis and Bordetella bronchiseptica contain transcriptionally silent pertussis toxin genes. J Bacteriol 1987; 169(6):2847-2853.

46. Mattoo S, Foreman-Wykert AK, Cotter PA, Miller JF: Mechanisms of Bordetella pathogenesis. Front Biosci 2001; 6:E168-E186.

47. Diavatopoulos DA, Cummings CA, Schouls LM, et al: Bordetella pertussis, the causative agent of whooping cough, evolved from a distinct, human-associated lineage of B. bronchiseptica. PLoS Pathog 2005; 1(4):e45.

48. Tang YW, Hopkins MK, Kolbert CP, et al: Bordetella holmesii-like organisms associated with septicemia, endocarditis, and respiratory failure. Clin Infect Dis 1998; 26(2):389-392.

49. Yih WK, Silva EA, Ida J, Harrington N, et al: Bordetella holmesii-like organisms isolated from Massachusetts patients with pertussis-like symptoms. Emerg Infect Dis 1999; 5(3):441-443.

50. Lindquist SW, Weber DJ, Mangum ME, et al: Bordetella holmesii sepsis in an asplenic adolescent. Pediatr Infect Dis J 1995; 14(9):813-815.

51. Shepard CW, Daneshvar MI, Kaiser RM, et al: Bordetella holmesii bacteremia: a newly recognized clinical entity among asplenic patients. Clin Infect Dis 2004; 38(6):799-804.

52. Cookson BT, Vandamme P, Carlson LC, et al: Bacteremia caused by a novel Bordetella species, ‘B. hinzii.’. J Clin Microbiol 1994; 32(10):2569-2571.

53. Funke G, Hess T, von Graevenitz A, Vandamme P: Characteristics of Bordetella hinzii strains isolated from a cystic fibrosis patient over a 3-year period. J Clin Microbiol 1996; 34(4):966-969.

54. Tuomanen E: Bordetella pertussis adhesins. In: Wardlaw AC, Parton R, ed. Pathogenesis and Immunity in Pertussis, New York: John; 1988:75-94.

55. Weiss A: Mucosal immune defenses and the response of Bordetella pertussis. ASM News 1997; 63:22-28.

56. Sato H, Sato Y: Relationship between structure and biological and protective activities of pertussis toxin. Dev Biol Stand 1991; 73:121-132.

87 57. Farizo KM, Huang T, Burns DL: Importance of holotoxin assembly in PT-mediated secretion of pertussis toxin from Bordetella pertussis. Infect Immun 2000; 68(7):4049-4054.

58. Tamura M, Nogimori K, Murai S, et al: Subunit structure of islet-activating protein, pertussis toxin, in conformity with the A-B model. Biochemistry 1982; 21(22):5516-5522.

59. Halperin SA, Issekutz TB, Kasina A: Modulation of Bordetella pertussis infection with monoclonal antibodies to pertussis toxin. J Infect Dis 1991; 163(2):355-361.

60. Nencioni L, Pizza MG, Volpini G, et al: Properties of the B oligomer of pertussis toxin. Infect Immun 1991; 59(12):4732- 4734.

61. Watanabe M: Biological activities of pertussigen from Bordetella pertussis strains of various agglutinogen types. Microbiol Immunol 1984; 28(5):509-515.

62. Hausman SZ, Cherry JD, Heininger U, et al: Analysis of proteins encoded by the ptx and ptl genes of Bordetella bronchiseptica and Bordetella parapertussis. Infect Immun 1996; 64(10):4020-4026.

63. Kirimanjeswara GS, Agosto LM, Kennett MJ, et al: Pertussis toxin inhibits neutrophil recruitment to delay antibody- mediated clearance of Bordetella pertussis. J Clin Invest 2005; 115(12):3594-3601.

64. Carbonetti NH, Artamonova GV, Mays RM, Worthington ZE: Pertussis toxin plays an early role in respiratory tract colonization by Bordetella pertussis. Infect Immun 2003; 71(11):6358-6366.

65. Carbonetti NH, Artamonova GV, Andreasen C, Bushar N: Pertussis toxin and adenylate cyclase toxin provide a one-two punch for establishment of Bordetella pertussis infection of the respiratory tract. Infect Immun 2005; 73(5):2698-2703.

66. Toyota T, Kai Y, Kakizaki M, et al: Effects of islet-activating protein (IAP) on blood glucose and plasma insulin in healthy volunteers (phase 1 studies). Tohoku J Exp Med 1980; 130(2):105-116.

67. Pittman M: The concept of pertussis as a toxin-mediated disease. Pediatr Infect Dis 1984; 3(5):467-486.

68. Sato H, Sato Y: Bordetella pertussis infection in mice: correlation of specific antibodies against two antigens, pertussis toxin, and filamentous hemagglutinin with mouse protectivity in an intracerebral or aerosol challenge system. Infect Immun 1984; 46(2):415-421.

69. Arciniega JL, Shahin RD, Burnette WN, et al: Contribution of the B oligomer to the protective activity of genetically attenuated pertussis toxin. Infect Immun 1991; 59(10):3407-3410.

70. McGuirk P, McCann C, Mills KH: Pathogen-specific T regulatory 1 cells induced in the respiratory tract by a bacterial molecule that stimulates interleukin 10 production by dendritic cells: a novel strategy for evasion of protective T helper type 1 responses by Bordetella pertussis. J Exp Med 2002; 195(2):221-231.

71. Abramson T, Kedem H, Relman DA: Proinflammatory and proapoptotic activities associated with Bordetella pertussis filamentous hemagglutinin. Infect Immun 2001; 69(4):2650-2658.

72. Tuomanen E, Weiss A, Rich R, et al: Filamentous hemagglutinin and pertussis toxin promote adherence of Bordetella pertussis to cilia. Dev Biol Stand 1985; 61:197-204.

73. Tuomanen E, Weiss A: Characterization of two adhesins of Bordetella pertussis for human ciliated respiratory-epithelial cells. J Infect Dis 1985; 152(1):118-125.

74. Oda M, Cowell JL, Burstyn DG, Manclark CR: Protective activities of the filamentous hemagglutinin and the lymphocytosis-promoting factor of Bordetella pertussis in mice. J Infect Dis 1984; 150(6):823-833.

75. He Q, Viljanen MK, Olander RM, et al: Antibodies to filamentous hemagglutinin of Bordetella pertussis and protection against whooping cough in schoolchildren. J Infect Dis 1994; 170(3):705-708.

88 76. Geuijen CA, Willems RJ, Bongaerts M, et al: Role of the Bordetella pertussis minor fimbrial subunit, FimD, in colonization of the mouse respiratory tract. Infect Immun 1997; 65(10):4222-4228.

77. Cotter PA, Yuk MH, Mattoo S, et al: Filamentous hemagglutinin of Bordetella bronchiseptica is required for efficient establishment of tracheal colonization. Infect Immun 1998; 66(12):5921-5929.

78. Stanbridge TN, Preston NW: Variation of serotype in strains of Bordetella pertussis. J Hyg (Lond) 1974; 73(2):305-310.

79. Preston NW, Stanbridge TN: Efficacy of pertussis vaccines: a brighter horizon. Br Med J 1972; 3(824):448-451.

80. Bronne-Shanbury C, Miller D, Standfast AF: The serotypes of Bordetella pertussis isolated in Great Britain between 1941 and 1968 and a comparison with the serotypes observed in other countries over this period. J Hyg (Lond) 1976; 76(2):265- 275.

81. Efficacy of whooping-cough vaccines used in the United Kingdon befroe 1968. Br Med J 1973; 1:259-262.

82. Preston NW: Prevalent serotypes of Bordetella pertussis in non-vaccinated communities. J Hyg (Lond) 1976; 77(1):85- 91.

83. Storsaeter J, Hallander HO, Gustafsson L, Olin P: Levels of anti-pertussis antibodies related to protection after household exposure to Bordetella pertussis. Vaccine 1998; 16(20):1907-1916.

84. Willems RJ, Kamerbeek J, Geuijen CA, et al: The efficacy of a whole cell pertussis vaccine and fimbriae against Bordetella pertussis and Bordetella parapertussis infections in a respiratory mouse model. Vaccine 1998; 16(4):410-416.

85. Rodriguez ME, Hellwig SM, Perez Vidakovics ML, et al: Bordetella pertussis attachment to respiratory epithelial cells can be impaired by fimbriae-specific antibodies. FEMS Immunol Med Microbiol 2006; 46(1):39-47.

86. WHO Expert Committee on Biological Standardization. Paper presented at: World Health Organ Tech Rep Ser, 1990.

87. Brennan MJ, Li ZM, Cowell JL, et al: Identification of a 69-kilodalton nonfimbrial protein as an agglutinogen of Bordetella pertussis. Infect Immun 1988; 56(12):3189-3195.

88. Novotny P, Chubb AP, Cownley K, Charles IG: Biologic and protective properties of the 69-kDa outer membrane protein of Bordetella pertussis: a novel formulation for an acellular pertussis vaccine. J Infect Dis 1991; 164(1):114-122.

89. Emsley P, McDermott G, Charles IG, et al: Crystallographic characterization of pertactin, a membrane-associated protein from Bordetella pertussis. J Mol Biol 1994; 235(2):772-773.

90. Leininger E, JG K, MJ B. Surface proteins of Bordetella pertussis: role in adherence. Proceedings of the Sixth International Symposium on Pertussis (DHHS Publication No. FDA 90–1164). Bethesda, MD: US Public Health Service; 1990:100–104.

91. Ewanowich CA, E L. Mechanisms of Bortella pertussis invasion of HeLa 229 cells. U.S Public Health Service. Proceedings of the Sixth International Symposium on Pertussis (DHHS Publication No. FDA 90–164. Bethesda, MD; 1990, 106–113

92. Trollfors B, Zackrisson G, Taranger J, Lagergard T: Serum antibodies against a 69-kilodalton outer-membrane protein, pertactin, from Bordetella pertussis in nonvaccinated children with and without a history of clinical pertussis. J Pediatr 1992; 120(6):924-926.

93. Thomas MG, Redhead K, Lambert HP: Human serum antibody responses to Bordetella pertussis infection and pertussis vaccination. J Infect Dis 1989; 159(2):211-218.

94. Shahin RD, Brennan MJ, Li ZM, et al: Characterization of the protective capacity and immunogenicity of the 69-kD outer membrane protein of Bordetella pertussis. J Exp Med 1990; 171(1):63-73.

89 95. Mooi FR, van Oirschot H, Heuvelman K, et al: Polymorphism in the Bordetella pertussis virulence factors P.69/pertactin and pertussis toxin in The Netherlands: temporal trends and evidence for vaccine-driven evolution. Infect Immun 1998; 66(2):670-675.

96. Njamkepo E, Rimlinger F, Thiberge S, Guiso N: Thirty-five years’ experience with the whole-cell pertussis vaccine in France: vaccine strains analysis and immunogenicity. Vaccine 2002; 20(9–10):1290-1294.

97. Weber C, Boursaux-Eude C, Coralie G, et al: Polymorphism of Bordetella pertussis isolates circulating for the last 10 years in France, where a single effective whole-cell vaccine has been used for more than 30 years. J Clin Microbiol 2001; 39(12):4396-4403.

98. King AJ, Berbers G, van Oirschot HF, et al: Role of the polymorphic region 1 of the Bordetella pertussis protein pertactin in immunity. Microbiology 2001; 147(Pt 11):2885-2895.

99. Mooi FR, van Loo IH, King AJ: Adaptation of Bordetella pertussis to vaccination: a cause for its reemergence. Emerg Infect Dis 2001; 7(3 Suppl):526-528.

100. Hallander HO, Advani A, Donnelly D, et al: Shifts of Bordetella pertussis variants in Sweden from 1970 to 2003, during three periods marked by different vaccination programs. J Clin Microbiol 2005; 43(6):2856-2865.

101. Mastrantonio P, Spigaglia P, van Oirschot H, et al: Antigenic variants in Bordetella pertussis strains isolated from vaccinated and unvaccinated children. Microbiology 1999; 145(Pt 8):2069-2075.

102. Mastrantonio P, Cerquetti M, Cardines R, et al: Immunogenicity issues in the quality control of the new acellular pertussis vaccines. Biologicals 1999; 27(2):119-121.

103. Poolman J. Efficacy of Infanrix in promoting lung cancer clearance of B. pertussis strains expressing pertactin antigenic variants in a mouse respiratory model. abstr 234. Abstracts of the 39th Interscience Conference on Antimicrobial Agents and Chemotherapy, September 1999. 1999:356.

104. Boursaux-Eude C, Thiberge S, Carletti G, Guiso N: Intranasal murine model of Bordetella pertussis infection: II. Sequence variation and protection induced by a tricomponent acellular vaccine. Vaccine 1999; 17(20–21):2651-2660.

105. Hewlett EL, VM G: Adenylate cyclase toxin of Bordetella pertussis. In: Wardlaw AC, Parton R, ed. Pathogenesis and Immunity in Pertussis, New York: John Wiley; 1998:193-209.

106. Hewlett EL, Donato GM, Gray MC: Macrophage cytotoxicity produced by adenylate cyclase toxin from Bordetella pertussis: more than just making cyclic. AMP! Mol Microbiol 2006; 59(2):447-459.

107. Weiss A, M G, N A. Investigation of the role of Bordetella pertussis virulence factors in disease. Proceedings of the Sixth International Symposium on Pertussis (DHHS Publication No. FDA 90–164. Bethesda, MD: US Public Health Service, 1990; 1990:202–205.

108. Arciniega JL, Hewlett EL, Johnson FD, et al: Human serologic response to envelope-associated proteins and adenylate cyclase toxin of Bordetella pertussis. J Infect Dis 1991; 163(1):135-142.

109. Guiso NMSMR: Bordetella pertussis adenylate cyclase: a protective antigen against lethality and bacterial colonizations in murine respiratory and intracerebral models. Proceedings of the Sixth International Symposium on Pertussis (DHHS Publication No. FDA 90–164, Bethesda, MD: US Public Health Service; 1990:207-231.

110. Cookson BT, Cho HL, Herwaldt LA, Goldman WE: Biological activities and chemical composition of purified tracheal cytotoxin of Bordetella pertussis. Infect Immun 1989; 57(7):2223-2229.

111. Goldman WE: Tracheal cytotoxin of Bordetella pertussis. In: Wardlaw AC, Parton R, ed. Pathogenesis and Immunity in Pertussis, New York: John Wiley; 1988:231-246.

112. Cookson BT, Cho HL, Herwaldt LA, Goldman WE: Biological activities and chemical composition of purified tracheal cytotoxin of Bordetella pertussis. Infect Immun 1989 Jul; 57(7):2223-2229.

90 113. Nakase Y, Endoh M: Heat-labile toxin of Bordetella pertussis endotoxin. In: Wardlaw AC, Parton R, ed. Pathogenesis and Immunity in Pertussis, New York: John Wiley; 1988:211-229.

114. Endoh M, Nagai M, Burns DL, et al: Effects of exogenous agents on the action of Bordetella parapertussis heat-labile toxin on guinea pig skin. Infect Immun 1990; 58(5):1456-1460.

115. Fernandez RC, Weiss AA: Cloning and sequencing of a Bordetella pertussis serum resistance locus. Infect Immun 1994; 62(11):4727-4738.

116. Elder KD, Harvill ET: Strain-dependent role of BrkA during Bordetella pertussis infection of the murine respiratory tract. Infect Immun 2004; 72(10):5919-5924.

117. Oliver DC, Fernandez RC: Antibodies to BrkA augment killing of Bordetella pertussis. Vaccine 2001; 20(1–2):235-241.

118. Barnes MG, Weiss AA: Growth phase influences complement resistance of Bordetella pertussis. Infect Immun 2002; 70(1):403-406.

119. Chaby R, Croff M: Lipopolysaccharides of Bordetella pertussis endotoxin. In: Wardlaw AC, Parton R, ed. Pathogenesis and Immunity in Pertussis, New York: John Wiley; 1988:247-271.

120. Harvill ET, Preston A, Cotter PA, et al: Multiple roles for Bordetella lipopolysaccharide molecules during respiratory tract infection. Infect Immun 2000; 68(12):6720-6728.

121. Baraff LJ, Manclark CR, Cherry JD, et al: Analyses of adverse reactions to diphtheria and tetanus toxoids and pertussis vaccine by vaccine lot, endotoxin content, pertussis vaccine potency and percentage of mouse weight gain. Pediatr Infect Dis J 1989; 8(8):502-507.

122. Weiss AA, Hewlett EL: Virulence factors of Bordetella pertussis. Annu Rev Microbiol 1986; 40:661-686.

123. Hewlett EL: Pertussis: current concepts of pathogenesis and prevention. Pediatr Infect Dis J 1997; 16(4 Suppl):S78- S84.

124. Zhang JM, Cowell JL, Steven AC, Manclark CR: Purification of serotype 2 fimbriae of Bordetella pertussis and their identification as a mouse protective antigen. Dev Biol Stand 1985; 61:173-185.

125. Confer DL, Eaton JW: Phagocyte impotence caused by an invasive bacterial adenylate cyclase. Science 1982; 217(4563):948-950.

126. Olson LC: Pertussis. Medicine (Baltimore) 1975; 54(6):427-469.

127. Muller FM, Hoppe JE, Wirsing von Konig CH: Laboratory diagnosis of pertussis: state of the art in 1997. J Clin Microbiol 1997; 35(10):2435-2443.

128. Hallander HO: Microbiological and serological diagnosis of pertussis. Clin Infect Dis 1999; 28(Suppl 2):S99-S106.

129. Broome CV, Fraser DW, English WJ: Pertussis–diagnostic methods and surveillance, Bethesda, Md., U. S. Dept. of Health, Education, and Welfare, Public Health Service, National Institutes of Health; Washington: for sale by the Supt of Docs, U. S. Govt Print Off, 1979.

130. Strebel PM, Cochi SL, Farizo KM, et al: Pertussis in Missouri: evaluation of nasopharyngeal culture, direct fluorescent antibody testing, and clinical case definitions in the diagnosis of pertussis. Clin Infect Dis 1993; 16(2):276-285.

131. Onorato IM, Wassilak SG: Laboratory diagnosis of pertussis: the state of the art. Pediatr Infect Dis J 1987; 6(2):145- 151.

132. Halperin SA, Bortolussi R, Wort AJ: Evaluation of culture, immunofluorescence, and serology for the diagnosis of pertussis. J Clin Microbiol 1989; 27(4):752-757.

91 133. Hallander HO, Reizenstein E, Renemar B, et al: Comparison of nasopharyngeal aspirates with swabs for culture of Bordetella pertussis. J Clin Microbiol 1993; 31(1):50-52.

134. Granstrom G, Wretlind B, Granstrom M: Diagnostic value of clinical and bacteriological findings in pertussis. J Infect 1991; 22(1):17-26.

135. Placebo-controlled trial of two acellular pertussis vaccines in Sweden–protective efficacy and adverse events. Ad Hoc Group for the Study of Pertussis Vaccines. Lancet 1988; 1(8592):955-960.

136. Heininger U, Schmidt-Schlapfer G, Cherry JD, Stehr K: Clinical validation of a polymerase chain reaction assay for the diagnosis of pertussis by comparison with serology, culture, and symptoms during a large pertussis vaccine efficacy trial. Pediatrics 2000; 105(3):E31.

137. Stadel AJ: Use of monoclonal fluorescent antibodies for the detection of B. pertussis and B. parapertussis. Am Clin Lab 2000; 19(3):14.

138. Ewanowich CA, Chui LW, Paranchych MG, et al: Major outbreak of pertussis in northern Alberta, Canada: analysis of discrepant direct fluorescent-antibody and culture results by using polymerase chain reaction methodology. J Clin Microbiol 1993; 31(7):1715-1725.

139. He Q, Mertsola J, Soini H, Viljanen MK: Sensitive and specific polymerase chain reaction assays for detection of Bordetella pertussis in nasopharyngeal specimens. J Pediatr 1994; 124(3):421-426.

140. Schlapfer G, Cherry JD, Heininger U, et al: Polymerase chain reaction identification of Bordetella pertussis infections in vaccinees and family members in a pertussis vaccine efficacy trial in Germany. Pediatr Infect Dis J 1995; 14(3):209-214.

141. Olcen P, Backman A, Johansson B, et al: Amplification of DNA by the polymerase chain reaction for the efficient diagnosis of pertussis. Scand J Infect Dis 1992; 24(3):339-345.

142. Reizenstein E, Lofdahl S, Granstrom M, et al: Evaluation of an improved DNA probe for diagnosis of pertussis. Diagn Microbiol Infect Dis 1992; 15(7):569-573.

143. Glare EM, Paton JC, Premier RR, et al: Analysis of a repetitive DNA sequence from Bordetella pertussis and its application to the diagnosis of pertussis using the polymerase chain reaction. J Clin Microbiol 1990; 28(9):1982-1987.

144. Edelman K, Nikkari S, Ruuskanen O, et al: Detection of Bordetella pertussis by polymerase chain reaction and culture in the nasopharynx of erythromycin-treated infants with pertussis. Pediatr Infect Dis J 1996; 15(1):54-57.

145. He Q, Schmidt-Schlapfer G, Just M, et al: Impact of polymerase chain reaction on clinical pertussis research: Finnish and Swiss experiences. J Infect Dis 1996; 174(6):1288-1295.

146. Knorr L, Fox JD, Tilley PA, Ahmed-Bentley J: Evaluation of real-time PCR for diagnosis of Bordetella pertussis infection. BMC Infect Dis 2006; 6:62.

147. Schmidt-Schlapfer G, Liese JG, Porter F, et al: Polymerase chain reaction (PCR) compared with conventional identification in culture for detection of Bordetella pertussis in 7153 children. Clin Microbiol Infect 1997; 3(4):462-467.

148. Sloan LM, Hopkins MK, Mitchell PS, et al: Multiplex LightCycler PCR assay for detection and differentiation of Bordetella pertussis and Bordetella parapertussis in nasopharyngeal specimens. J Clin Microbiol 2002; 40(1):96-100.

149. Kosters K, Riffelmann M, Wirsing von Konig CH: Evaluation of a real-time PCR assay for detection of Bordetella pertussis and B. parapertussis in clinical samples. J Med Microbiol 2001; 50(5):436-440.

150. Reischl U, Lehn N, Sanden GN, Loeffelholz MJ: Real-time PCR assay targeting IS481 of Bordetella pertussis and molecular basis for detecting Bordetella holmesii. J Clin Microbiol 2001; 39(5):1963-1966.

151. Tilley PA, Kanchana MV, Knight I, et al: Detection of Bordetella pertussis in a clinical laboratory by culture, polymerase chain reaction, and direct fluorescent antibody staining; accuracy, and cost. Diagn Microbiol Infect Dis 2000; 37(1):17-23.

92 152. Loeffelholz MJ, Thompson CJ, Long KS, Gilchrist MJ: Comparison of PCR, culture, and direct fluorescent-antibody testing for detection of Bordetella pertussis. J Clin Microbiol 1999; 37(9):2872-2876.

153. Templeton KE, Scheltinga SA, van der Zee A, et al: Evaluation of real-time PCR for detection of and discrimination between Bordetella pertussis, Bordetella parapertussis, and Bordetella holmesii for clinical diagnosis. J Clin Microbiol 2003; 41(9):4121-4126.

154. Muyldermans G, Soetens O, Antoine M, et al: External quality assessment for molecular detection of Bordetella pertussis in European laboratories. J Clin Microbiol 2005; 43(1):30-35.

155. Lievano FA, Reynolds MA, Waring AL, et al: Issues associated with and recommendations for using PCR to detect outbreaks of pertussis. J Clin Microbiol 2002; 40(8):2801-2805.

156. Klement E, Uliel L, Engel I, et al: An outbreak of pertussis among young Israeli soldiers. Epidemiol Infect 2003; 131(3):1049-1054.

157. Srugo I, Benilevi D, Madeb R, et al: Pertussis infection in fully vaccinated children in day-care centers, Israel. Emerg Infect Dis 2000; 6(5):526-529.

158. Fisher MC, Long SS, McGowan KL, et al: Outbreak of pertussis in a residential facility for handicapped people. J Pediatr 1989; 114(6):934-939.

159. Meade B, Mink C, CR M. Serodiagnoisis of pertussis. Proceedings of the Sixth International Symposium on Pertussis. DHHS Publication No. FDA 90–164. Bethesda, MD: US Public Health Service, 1990:322–329.

160. Wirsing von Konig CH, Gounis D, Laukamp S, et al: Evaluation of a single-sample serological technique for diagnosing pertussis in unvaccinated children. Eur J Clin Microbiol Infect Dis 1999; 18(5):341-345.

161. Simondon F, Iteman I, Preziosi MP, et al: Evaluation of an immunoglobulin G enzyme-linked immunosorbent assay for pertussis toxin and filamentous hemagglutinin in diagnosis of pertussis in Senegal. Clin Diagn Lab Immunol 1998; 5(2):130- 134.

162. Steketee RW, Burstyn DG, Wassilak SG, et al: A comparison of laboratory and clinical methods for diagnosing pertussis in an outbreak in a facility for the developmentally disabled. J Infect Dis 1988; 157(3):441-449.

163. Mink CM, Cherry JD, Christenson P, et al: A search for Bordetella pertussis infection in university students. Clin Infect Dis 1992; 14(2):464-471.

164. Addiss DG, Davis JP, Meade BD, et al: A pertussis outbreak in a Wisconsin nursing home. J Infect Dis 1991; 164(4):704-710.

165. Cattaneo LA, Reed GW, Haase DH, et al: The seroepidemiology of Bordetella pertussis infections: a study of persons ages 1–65 years. J Infect Dis 1996; 173(5):1256-1259.

166. Giammanco A, Chiarini A, Stroffolini T, et al: Seroepidemiology of pertussis in Italy. Rev Infect Dis 1991; 13(6):1216- 1220.

167. Cherry JD, Chang SJ, Klein D, et al: Prevalence of antibody to Bordetella pertussis antigens in serum specimens obtained from 1793 adolescents and adults. Clin Infect Dis 2004; 39(11):1715-1718.

168. Baughman AL, Bisgard KM, Edwards KM, et al: Establishment of diagnostic cutoff points for levels of serum antibodies to pertussis toxin, filamentous hemagglutinin, and fimbriae in adolescents and adults in the United States. Clin Diagn Lab Immunol 2004; 11(6):1045-1053.

169. Halperin SA, Bortolussi R, MacLean D, Chisholm N: Persistence of pertussis in an immunized population: results of the Nova Scotia Enhanced Pertussis Surveillance Program. J Pediatr 1989; 115(5 Pt 1):686-693.

170. Edwards KM: Is pertussis a frequent cause of cough in adolescents and adults. Should routine pertussis immunization be recommended? Clin Infect Dis 2001; 32(12):1698-1699.

93 171. Ward JI, Cherry JD, Chang SJ, et al: Efficacy of an acellular pertussis vaccine among adolescents and adults. N Engl J Med 2005; 353(15):1555-1563.

172. Meade BD, Deforest A, Edwards KM, et al: Description and evaluation of serologic assays used in a multicenter trial of acellular pertussis vaccines. Pediatrics 1995; 96(3 Pt 2):570-575.

173. Lynn F, Reed GF, Meade BD: A comparison of enzyme immunoassays used to measure serum antibodies to components of Bordetella pertussis. Dev Biol Stand 1997; 89:197-204.

174. Lynn F, Reed GF, Meade BD: Collaborative study for the evaluation of enzyme-linked immunosorbent assays used to measure human antibodies to Bordetella pertussis antigens. Clin Diagn Lab Immunol 1996; 3(6):689-700.

175. Reizenstein E, Hallander HO, Blackwelder WC, et al: Comparison of five calculation modes for antibody ELISA procedures using pertussis serology as a model. J Immunol Methods 1995; 183(2):279-290.

176. Marchant CD, Loughlin AM, Lett SM, et al: Pertussis in Massachusetts, 1981–1991: incidence, serologic diagnosis, and vaccine effectiveness. J Infect Dis 1994; 169(6):1297-1305.

177. Yih WK, Lett SM, des Vignes FN, et al: The increasing incidence of pertussis in Massachusetts adolescents and adults, 1989–1998. J Infect Dis 2000; 182(5):1409-1416.

178. Strebel P, Nordin J, Edwards K, et al: Population-based incidence of pertussis among adolescents and adults, Minnesota, 1995–1996. J Infect Dis 2001; 183(9):1353-1359.

179. de Melker HE, Versteegh FG, Conyn-Van Spaendonck MA, et al: Specificity and sensitivity of high levels of immunoglobulin G antibodies against pertussis toxin in a single serum sample for diagnosis of infection with Bordetella pertussis. J Clin Microbiol 2000; 38(2):800-806.

180. Hallander HO: Diagnostic pertussis serology in the recent clinical efficacy studies of acellular vaccines. Dev Biol Stand 1997; 89:205-212.

181. Tiwari T, Murphy TV, Moran J: Recommended antimicrobial agents for the treatment and postexposure prophylaxis of pertussis: 2005 CDC Guidelines. MMWR Recomm Rep 2005; 54(RR-14):1-16.

182. Halperin SA, Bortolussi R, Langley JM, et al: Seven days of erythromycin estolate is as effective as fourteen days for the treatment of Bordetella pertussis infections. Pediatrics 1997; 100(1):65-71.

183. Bass JW, Klenk EL, Kotheimer JB, et al: Antimicrobial treatment of pertussis. J Pediatr 1969; 75(5):768-781.

184. Hewlett EL: Bordetella species. In: Mandell G, ed. Douglas and Bennett's Principles and Practice of Infectious Diseases, 4th ed.. New York: Churchill Livingstone; 1995.

185. Mortimer Jr EA, Jones PK: An evaluation of pertussis vaccine. Rev Infect Dis 1979; 1(6):927-934.

186. Peter G HC, Halsey NA, et al: Report of the Committee on Infectious Diseases, 24th ed. American Academy of Pedicitrics; 1997.

187. Kawai H, Aoyama T, Goto A, et al: Evaluation of pertussis treatment with erythromycin ethylsuccinate and stearate according to age. Kansenshogaku Zasshi 1994; 68(11):1324-1329.

188. Aoyama T, Sunakawa K, Iwata S, et al: Efficacy of short-term treatment of pertussis with clarithromycin and azithromycin. J Pediatr 1996; 129(5):761-764.

189. Halperin SA, Bortolussi R, Langley JM, et al: A randomized, placebo-controlled trial of erythromycin estolate chemoprophylaxis for household contacts of children with culture-positive Bordetella pertussis infection. Pediatrics 1999; 104(4):e42.

190. Bortolussi R, Miller B, Ledwith M, Halperin S: Clinical course of pertussis in immunized children. Pediatr Infect Dis J 1995; 14(10):870-874.

94 191. Kwantes W, Joynson DH, Williams WO: Bordetella pertussis isolation in general practice: 1977–79 whooping cough epidemic in West Glamorgan. J Hyg (Lond) 1983; 90(2):149-158.

192. Henry R, Dorman D, Skinner J, Mellis C: Limitations of erythromycin in whooping cough. Med J Aust 1981; 2(2):108- 109.

193. Hoppe JE, Rahimi-Galougahi E, Seibert G: In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to four fluoroquinolones (levofloxacin, d-ofloxacin, ofloxacin, and ciprofloxacin), cefpirome, and meropenem. Antimicrob Agents Chemother 1996; 40(3):807-808.

194. Hoppe JE, Bryskier A: In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to two ketolides (HMR 3004 and HMR 3647), four macrolides (azithromycin, clarithromycin, erythromycin A, and roxithromycin), and two ansamycins (rifampin and rifapentine). Antimicrob Agents Chemother 1998; 42(4):965-966.

195. Langley JM, Halperin SA, Boucher FD, Smith B: Azithromycin is as effective as and better tolerated than erythromycin estolate for the treatment of pertussis. Pediatrics 2004; 114(1):e96-e101.

196. Prevention CfDC : Hypertrophic pyloric stenosis in infants following pertussis prophylasis with erythromycin Knoxville, Tennessee. JAMA 2000; 283:471-472.

197. Honein MA, Paulozzi LJ, Himelright IM, et al: Infantile hypertrophic pyloric stenosis after pertussis prophylaxis with erythromcyin: a case review and cohort study. Lancet 1999; 354(9196):2101-2105.

198. CDC : Erythromycin-resistant Bordetella pertussis Yuma County, Arizona, May-October, 1994. JAMA 1995; 273:13-14.

199. Gordon KA, Fusco J, Biedenbach DJ, et al: Antimicrobial susceptibility testing of clinical isolates of Bordetella pertussis from northern California: report from the SENTRY Antimicrobial Surveillance Program. Antimicrob Agents Chemother 2001; 45(12):3599-3600.

200. Korgenski EK, Daly JA: Surveillance and detection of erythromycin resistance in Bordetella pertussis isolates recovered from a pediatric population in the Intermountain West region of the United States. J Clin Microbiol 1997; 35(11):2989-2991.

201. Bartkus JM, Juni BA, Ehresmann K, et al: Identification of a mutation associated with erythromycin resistance in Bordetella pertussis: implications for surveillance of antimicrobial resistance. J Clin Microbiol 2003; 41(3):1167-1172.

202. Bartkus J, Juni BA, Ehresman K. Proposed mechanism of erythromycin resistance in Bordetella pertussi [abst C1– 1817]. Paper presented at: 41st Interscience Conference on Antimicrobial Agents and Chemotherapy; December 16–19, 2001; Chicago, IL.

203. Beneson AS: Control of Communicable Disease Manual, 16th ed.. Washington, DC, American Public Health Association, 1995.

204. Weber DJ, Rutala WA: Management of healthcare workers exposed to pertussis. Infect Control Hosp Epidemiol 1994; 15(6):411-415.

205. Decker MD SW: Nosocomial Diseases of health care workers spread by airborne or contact route (other than tuberculosis), Baltimore, Williams & Wilkins, 1996.

206. Wirsing von Konig CH, Schmitt HJ, Bogaerts H, et al: Factors influencing the analysis of secondary prevention of pertussis. Dev Biol Stand 1997; 89:175-179.

207. De Serres G, Boulianne N, Duval B: Field effectiveness of erythromycin prophylaxis to prevent pertussis within families. Pediatr Infect Dis J 1995; 14(11):969-975.

208. Fine PE, Clarkson JA: The recurrence of whooping cough: possible implications for assessment of vaccine efficacy. Lancet 1982; 1(8273):666-669.

209. Farizo KM, Cochi SL, Zell ER, et al: Epidemiological features of pertussis in the United States, 1980–1989. Clin Infect Dis 1992; 14(3):708-719.

95 210. Guris D, Strebel PM, Bardenheier B, et al: Changing epidemiology of pertussis in the United States: increasing reported incidence among adolescents and adults, 1990–1996. Clin Infect Dis 1999; 28(6):1230-1237.

211. Cherry JD: The epidemiology of pertussis and pertussis immunization in the United Kingdom and the United States: a comparative study. Curr Probl Pediatr 1984; 14(2):1-78.

212. Kanai K: Japan's experience in pertussis epidemiology and vaccination in the past thirty years. Jpn J Med Sci Biol 1980; 33(3):107-143.

213. Cherry JD, Baraff LJ, Hewlett E: The past, present, and future of pertussis. The role of adults in epidemiology and future control. West J Med 1989; 150(3):319-328.

214. Cherry JD: Pertussis in adults. Ann Intern Med 1998; 128(1):64-66.

215. Luttinger P: The epidemiology of pertussis. Am J Dis Child 1916; 12:290-315.

216. Friedlander A: Whooping cough. Pediatrics 1925; 11:128-147.

217. Pertussis—United States, 2001–2003. MMWR Morb Mortal Wkly Rep 2005; 54(50):1283-1286.

218. Lambert HJ: Epidemiology of a small pertussis outbreak in Kent County, Michigan. Public Health Rep 1965; 80:365- 369.

219. Cherry JD, Beer T, Chartrand SA, et al: Comparison of values of antibody to Bordetella pertussis antigens in young German and American men. Clin Infect Dis 1995; 20(5):1271-1274.

220. Linnemann Jr CC, Bass JW, Smith MH: The carrier state in pertussis. Am J Epidemiol 1968; 88(3):422-427.

221. Lambert HP: The carrier state: Bordetella pertussis. J Antimicrob Chemother 1986; 18(Suppl A):13-16.

222. Rosenthal S, Strebel P, Cassiday P, et al: Pertussis infection among adults during the 1993 outbreak in Chicago. J Infect Dis 1995; 171(6):1650-1652.

223. Christie CD, Marx ML, Marchant CD, Reising SF: The 1993 epidemic of pertussis in Cincinnati. Resurgence of disease in a highly immunized population of children. N Engl J Med 1994; 331(1):16-21.

224. Resurgence of pertussis—United States, 1993. MMWR Morb Mortal Wkly Rep 1993; 42(49):952-953, 959–960.

225. Pertussis outbreak—Vermont, 1996. MMWR Morb Mortal Wkly Rep 1997; 46(35):822-826.

226. Edwards KM, Decker MD, Halsey NA, et al: Differences in antibody response to whole-cell pertussis vaccines. Pediatrics 1991; 88(5):1019-1023.

227. Edwards KM, Decker MD: Acellular pertussis vaccines for infants. N Engl J Med 1996; 334(6):391-392.

228. Stehr K, Cherry JD, Heininger U, et al: A comparative efficacy trial in Germany in infants who received either the Lederle/Takeda acellular pertussis component DTP (DTaP) vaccine, the Lederle whole-cell component DTP vaccine, or DT vaccine. Pediatrics 1998; 101(1 Pt 1):1-11.

229. Gustafsson L, Hallander HO, Olin P, et al: A controlled trial of a two-component acellular, a five-component acellular, and a whole-cell pertussis vaccine. N Engl J Med 1996; 334(6):349-355.

230. Greco D, Salmaso S, Mastrantonio P, et al: A controlled trial of two acellular vaccines and one whole-cell vaccine against pertussis. Progetto Pertosse Working Group. N Engl J Med 1996; 334(6):341-348.

231. Pertussis—United States, January 1992-June 1995. MMWR Morb Mortal Wkly Rep 1995; 44(28):525-529.

232. Davis SF, Strebel PM, Cochi SL, et al: Pertussis surveillance—United States, 1989–1991. MMWR CDC Surveill Summ 1992; 41(8):11-19.

96 233. He Q, Viljanen MK, Nikkari S, et al: Outcomes of Bordetella pertussis infection in different age groups of an immunized population. J Infect Dis 1994; 170(4):873-877.

234. Biellik RJ, Patriarca PA, Mullen JR, et al: Risk factors for community- and household-acquired pertussis during a large- scale outbreak in central Wisconsin. J Infect Dis 1988; 157(6):1134-1141.

235. Mink CA, Sirota NM, Nugent S: Outbreak of pertussis in a fully immunized adolescent and adult population. Arch Pediatr Adolesc Med 1994; 148(2):153-157.

236. School-associated pertussis outbreak—Yavapai County, Arizona, September 2002–February 2003. MMWR Morb Mortal Wkly Rep 2004; 53(10):216-219.

237. Davis JP: Clinical and economic effects of pertussis outbreaks. Pediatr Infect Dis J 2005; 24(6 Suppl):S109-S116.

238. Elliott E, McIntyre P, Ridley G, et al: National study of infants hospitalized with pertussis in the acellular vaccine era. Pediatr Infect Dis J 2004; 23(3):246-252.

239. Robertson PW, Goldberg H, Jarvie BH, et al: Bordetella pertussis infection: a cause of persistent cough in adults. Med J Aust 1987; 146(10):522-525.

240. Wright SW, Edwards KM, Decker MD, Zeldin MH: Pertussis infection in adults with persistent cough. JAMA 1995; 273(13):1044-1046.

241. Nennig ME, Shinefield HR, Edwards KM, et al: Prevalence and incidence of adult pertussis in an urban population. JAMA 1996; 275(21):1672-1674.

242. Campins-Marti M, Cheng HK, Forsyth K, et al: Recommendations are needed for adolescent and adult pertussis immunisation: rationale and strategies for consideration. Vaccine 2001; 20(5–6):641-646.

243. Lee GM, Lett S, Schauer S, et al: Societal costs and morbidity of pertussis in adolescents and adults. Clin Infect Dis 2004; 39(11):1572-1580.

244. Purdy KW, Hay JW, Botteman MF, Ward JI: Evaluation of strategies for use of acellular pertussis vaccine in adolescents and adults: a cost-benefit analysis. Clin Infect Dis 2004; 39(1):20-28.

245. Van Rie A, Hethcote HW: Adolescent and adult pertussis vaccination: computer simulations of five new strategies. Vaccine 2004; 22(23–24):3154-3165.

246. Global Programme on Vaccines Paper presented at: State of the World's Vaccines and Immunization. World Health Organization, 1996; New York

247. Crowcroft NS, Stein C, Duclos P, Birmingham M: How best to estimate the global burden of pertussis. Lancet Infect Dis 2003; 3(7):413-418.

248. Van Savage J, Decker MD, Edwards KM, et al: Natural history of pertussis antibody in the infant and effect on vaccine response. J Infect Dis 1990; 161(3):487-492.

249. Healy CM, Munoz FM, Rench MA, et al: Prevalence of pertussis antibodies in maternal delivery, cord, and infant serum. J Infect Dis 2004; 190(2):335-340.

250. Lichty JA, Slavin B, Bradford WL: An attempt to increase resistance to pertussis in newborn infants by immunizing their mothers during pregnancy. J Clin Invest 1938; 17(5):613-621.

251. Pertussis antibodies in pregnant women : Protective, agglutinating and complement fixing antibodies before and after vaccination. Am J Dis Child 1942; 64:608-617.

252. Cohen P, Scadron S: The Placental transmission of protective antibodies against whooping cough by inoculation of the pregnant mother. JAMA 1943; 121:656-662.

97 253. Kendrick P, Thompson M, Eldering G: Immunity response of mothers and babies to injections of pertussis vaccine during pregnancy. Am J Dis Child 1946; 70:25-28.

254. Englund JA, Anderson EL, Reed GF, et al: The effect of maternal antibody on the serologic response and the incidence of adverse reactions after primary immunization with acellular and whole-cell pertussis vaccines combined with diphtheria and tetanus toxoids. Pediatrics 1995; 96(3 Pt 2):580-584.

255. Elahi S, Buchanan RM, Babiuk LA, Gerdts V: Maternal immunity provides protection against pertussis in newborn piglets. Infect Immun 2006; 74(5):2619-2627.

256. Bradford W: Use of convalescent blood in whooping cough. Am J Dis Child 1935; 50:918-928.

257. Balagtas RC, Nelson KE, Levin S, Gotoff SP: Treatment of pertussis with pertussis immune globulin. J Pediatr 1971; 79(2):203-208.

258. Morris D, McDonald JC: Failure of hyperimmune gamma globulin to prevent whooping cough. Arch Dis Child 1957; 32(163):236-239.

259. Granstrom M, Olinder-Nielsen AM, Holmblad P, et al: Specific immunoglobulin for treatment of whooping cough. Lancet 1991; 338(8777):1230-1233.

260a. Halperin SA, Vaudry W, Boucher FD, Mackintosh K, Waggener TB, Smith B: Is pertussis immune globulin efficacious for the treatment of hospitalized infants with pertussis? No answer yet. Pediatric Investigators Collaborative Network on Infections in Canada. Pediatr Infect Dis J 2007 Jan; 26(1):79-81.

261. Madsen T: Vaccination against whooping cough. JAMA 1933; 101:187-188.

262. Kendrick P, Eldering G, Dixon M: Mouse protection tests in the study of pertussis vaccine: a comparative series using intrcerebral route for challenge. Am J Public Health 1947; 37:803-810.

263. Eldering G: Symposium on pertussis immunization, in honor of Dr. Pearl L. Kendrick in her eightietn year: historical notes on pertussis immunization. Health Lab Sci 1971; 8(4):200-205.

264. Vaccination against whooping-cough; relation between protection in children and results of laboratory tests; a report to the Whooping-cough Immunization Committee of the Medical Research Council and to the medical officers of health for Cardiff, Leeds, Leyton, Manchester, Middlesex, Oxford, Poole, Tottenham, Walthamstow, and Wembley. BMJ 1956.454- 462.

265. Sato Y, Kimura M, Fukumi H: Development of a pertussis component vaccine in Japan. Lancet 1984; 1(8369):122- 126.

266. Kimura M, Hikino N: Results with a new DTP vaccine in Japan. Dev Biol Stand 1985; 61:545-561.

267. Noble GR, Bernier RH, Esber EC, et al: Acellular and whole-cell pertussis vaccines in Japan. Report of a visit by US scientists. JAMA 1987; 257(10):1351-1356.

268. Aoyama T, Murase Y, Gonda T, Iwata T: Type-specific efficacy of acellular pertussis vaccine. Am J Dis Child 1988; 142(1):40-42.

269. Kimura M, Kuno-Sakai H: Current epidemiology of pertussis in Japan. Pediatr Infect Dis J 1990; 9(10):705-709.

270. Kimura M: Japanese clinical experiences with acellular pertussis vaccines. Dev Biol Stand 1991; 73:5-9.

271. Kuno-Sakai H, Kimura M: Safety and efficacy of acellular pertussis vaccine in Japan, evaluated by 23 years of its use for routine immunization. Pediatr Int 2004; 46(6):650-655.

272. Edwards KM, Meade BD, Decker MD, et al: Comparison of 13 acellular pertussis vaccines: overview and serologic response. Pediatrics 1995; 96(3 Pt 2):548-557.

98 273. Guiso N, Capiau C, Carletti G, et al: Intranasal murine model of Bordetella pertussis infection. I. Prediction of protection in human infants by acellular vaccines. Vaccine 1999; 17(19):2366-2376.

274. Edwards K, Decker M, Mortimer EA: Pertussis vaccine. In: Plotkin S, Mortimer Jr EA, Orenstein WA, ed. Vaccines, 3rd ed. Philadelphia: WB Saunders; 1999:293-344.

275. Greenberg DP, Pickering LK, Senders SD, et al: Interchangeability of 2 diphtheria-tetanus-acellular pertussis vaccines in infancy. Pediatrics 2002; 109(4):666-672.

276. Hinman AR, Koplan JP: Pertussis and pertussis vaccine. Reanalysis of benefits, risks, and costs. JAMA 1984; 251(23):3109-3113.

277. Miller DL, Alderslade R, Ross EM: Whooping cough and whooping cough vaccine: the risks and benefits debate. Epidemiol Rev 1982; 4:1-24.

278. Kendrick P, Eldering G: Progress report on pertussis immunization. Am J Public Health 1936; 26:8-12.

279. Sauer L: Whooping Cough: new phases of the work of immunizations and prophylaxis. JAMA 1939; 112:305-308.

280. Baker JD, Halperin SA, Edwards K, et al: Antibody response to Bordetella pertussis antigens after immunization with American and Canadian whole-cell vaccines. J Pediatr 1992; 121(4):523-527.

281. Steinhoff MC, Reed GF, Decker MD, et al: A randomized comparison of reactogenicity and immunogenicity of two whole-cell pertussis vaccines. Pediatrics 1995; 96(3 Pt 2):567-570.

282. Doull J, Shibley G, McClelland J: Active immunization against whooping cough: interim report of the Cleveland experience. Am J Public Health 1936; 26:1097-1105.

283. Sako W: Studies on pertussis immunization. J Pediatr 1947; 30:29-40.

284. Vaccination against whooping-cough the final report to the Whooping-Cough Immunization Committee of the Medical Research Council and to the medical officers of health for Battersea and Wandsworth, Bradford, Liverpool, and Newcastle. BMJ 1959; 46(5128):994-1000.

285. Schmitt HJ, von Konig CH, Neiss A, et al: Efficacy of acellular pertussis vaccine in early childhood after household exposure. JAMA 1996; 275(1):37-41.

286. Liese JG, Meschievitz CK, Harzer E, et al: Efficacy of a two-component acellular pertussis vaccine in infants. Pediatr Infect Dis J 1997; 16(11):1038-1044.

287. Lederle Laboratories : ACEL-MUNE product labeling, Montvale, NJ, Medical Economics Company, 1997.

288. Simondon F, Preziosi MP, Yam A, et al: A randomized double-blind trial comparing a two-component acellular to a whole-cell pertussis vaccine in Senegal. Vaccine 1997; 15(15):1606-1612.

289. Ramsay ME, Farrington CP, Miller E: Age-specific efficacy of pertussis vaccine during epidemic and non-epidemic periods. Epidemiol Infect 1993; 111(1):41-48.

290. White JM, Fairley CK, Owen D, et al: The effect of an accelerated immunisation schedule on pertussis in England and Wales. Commun Dis Rep CDR Rev 1996; 6(6):R86-R91.

291. Miller E, Ashworth LA, Redhead K, et al: Effect of schedule on reactogenicity and antibody persistence of acellular and whole-cell pertussis vaccines: value of laboratory tests as predictors of clinical performance. Vaccine 1997; 15(1):51-60.

292. Lautrop H, Mikkelsen OS: [The effect of prophylactic whooping-cough vaccination. An attempt at an evaluation based on experiences in Denmark]. Ugeskr Laeger 1969; 131(17):735-741.

293. Sutter RW, Cochi SL: Pertussis hospitalizations and mortality in the United States, 1985–1988. Evaluation of the completeness of national reporting. JAMA 1992; 267(3):386-391.

99 294. Dauer C: Reported whooping cough morbidity and mortality in the United States. Public Health Rep 1943; 58:661-676.

295. Kimura M, Kuno-Sakai H: Immunization system in Japan: its history and present situation. Acta Paediatr Jpn 1988; 30(2):109-126.

296. Stuart-Harris Experiences of pertussis in the United Kingdom. Paper presented at: International Symposium on Pertussis, 1979; Bethesda, MD.

297. Romanus V, Jonsell R, Bergquist SO: Pertussis in Sweden after the cessation of general immunization in 1979. Pediatr Infect Dis J 1987; 6(4):364-371.

298. Storsaeter J, Olin P: Relative efficacy of two acellular pertussis vaccines during three years of passive surveillance. Vaccine 1992; 10(3):142-144.

299. Taranger J, Trollfors B, Bergfors E, et al: Immunologic and epidemiologic experience of vaccination with a monocomponent pertussis toxoid vaccine. Pediatrics 2001; 108(6):E115.

300. Baron S, Njamkepo E, Grimprel E, et al: Epidemiology of pertussis in French hospitals in 1993 and 1994: thirty years after a routine use of vaccination. Pediatr Infect Dis J 1998; 17(5):412-418.

301. Pollard R: Relation between vaccination and notification rates for whooping cough in England and Wales. Lancet 1980; 1(8179):1180-1182.

302. Onorato IM, Wassilak SG, Meade B: Efficacy of whole-cell pertussis vaccine in preschool children in the United States. JAMA 1992; 267(20):2745-2749.

303. Vesselinova-Jenkins CK, Newcombe RG, Gray OP, et al: The effects of immunisation upon the natural history of pertussis. A family study in the Cardiff area. J Epidemiol Community Health 1978; 32(3):194-199.

304. Grob PR, Crowder MJ, Robbins JF: Effect of vaccination on severity and dissemination of whooping cough. BMJ (Clin Res Ed) 1981; 282(6280):1925-1928.

305. Preziosi MP, Halloran ME: Effects of pertussis vaccination on disease: vaccine efficacy in reducing clinical severity. Clin Infect Dis 2003; 37(6):772-779.

306. Preziosi MP, Halloran ME: Effects of pertussis vaccination on transmission: vaccine efficacy for infectiousness. Vaccine 2003; 21(17–18):1853-1861.

307. Cvjetanovic B, Grab B, Uemura K: Diphtheria and whooping cough: diseases affecting a paticular age group. Bull World Health Organ 1978; 56(Suppl 1):103-133.

308. Fox JP, Elveback L, Scott W, et al: Herd immunity: basic concept and relevance to public health immunization practices. 1971. Am J Epidemiol 1995; 141(3):187-197; discussion 185–186.

309. Feikin DR, Lezotte DC, Hamman RF, et al: Individual and community risks of measles and pertussis associated with personal exemptions to immunization. JAMA 2000; 284(24):3145-3150.

310. Jenkinson D: Duration of effectiveness of pertussis vaccine: evidence from a 10 year community study. BMJ (Clin Res Ed) 1988; 296(6622):612-614.

311. Fine PE, Clarkson JA: Reflections on the efficacy of pertussis vaccines. Rev Infect Dis 1987; 9(5):866-883.

312. Weiss E, Kendrick P: The effectiveness of pertussis vaccine: an application of Sargent and Merrell's method of measurement. Am J Hyg 1943; 38:306-309.

313. Howson CP, Fineberg HV: Adverse events following pertussis and rubella vaccines. Summary of a report of the Institute of Medicine. JAMA 1992; 267(3):392-396.

100 314. Howe Stratton CJ, Johnston RB: DPT Vaccine and Chronic Nervous System Dysfunction: A New Analysis, Washington, DC, National Academy Press, 1994.

315. Howson CP, Howe BJ, Fineberg HV. AdverseEffects of Pertussis and Rubella Vaccines: Report of the committee to review the Adverse Consequences of Pertussis and Rubella Vaccines Institute of Medicine. Paper presented at: Washington, DC, 1991.

316. Mortimer E: Pertussis. In: Plotkin S, Mortimer E, ed. Vaccines, 2nd ed.. Philadelphia: WB Saunders; 1994.

317. Diphtheria, tetanus, and pertussis recommendations for vaccine use and other preventive measures. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR Recomm Rep 1991; 40(RR-10):1- 28.

318. Cadoz M, Arminjon F, Quentin-Millet MJ: Safety and immunogenicity of Merieux acellular pertussis in adult volunteers. In transcript of the Workshop on Acellular Pertussis Vaccines, Washington, DC: U.S. Department of Health and Human Services; 1986:131-134.

319. Cody CL, Baraff LJ, Cherry JD, et al: Nature and rates of adverse reactions associated with DTP and DT immunizations in infants and children. Pediatrics 1981; 68(5):650-660.

320. Decker MD, Edwards KM, Steinhoff MC, et al: Comparison of 13 acellular pertussis vaccines: adverse reactions. Pediatrics 1995; 96(3 Pt 2):557-566.

321. Baraff LJ, Cody CL, Cherry JD: DTP-associated reactions: an analysis by injection site, manufacturer, prior reactions, and dose. Pediatrics 1984; 73(1):31-36.

322. Pichichero ME, Christy C, Decker MD, et al: Defining the key parameters for comparing reactions among acellular and whole-cell pertussis vaccines. Pediatrics 1995; 96(3 Pt 2):588-592.

323. Deloria MA, Blackwelder WC, Decker MD, et al: Association of reactions after consecutive acellular or whole-cell pertussis vaccine immunizations. Pediatrics 1995; 96(3 Pt 2):592-594.

324. Hirtz DG, Nelson KB, Ellenberg JH: Seizures following childhood immunizations. J Pediatr 1983; 102(1):14-18.

325. Walker AM, Jick H, Perera DR, et al: Neurologic events following diphtheria-tetanus-pertussis immunization. Pediatrics 1988; 81(3):345-349.

326. Griffin MR, Ray WA, Mortimer EA, et al: Risk of seizures and encephalopathy after immunization with the diphtheria- tetanus-pertussis vaccine. JAMA 1990; 263(12):1641-1645.

327. Stetler HC, Orenstein WA, Bart KJ, et al: History of convulsions and use of pertussis vaccine. J Pediatr 1985; 107(2):175-179.

328. Bellman M, Ross E: Pertussis immunizations and fits. In: Ross E, Reynolds E, ed. Peadiatric Perspectives on Epilepsy, New York: John Wiley; 1985.

329. Livengood JR, Mullen JR, White JW, et al: Family history of convulsions and use of pertussis vaccine. J Pediatr 1989; 115(4):527-531.

330. Center for Biologics Evaluation and Research (U.S.). Proceedings of the Sixth International Symposium on Pertussis, Jack Masur Auditorium, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, September 26–28, 1990. Bethesda, Md.: Dept. of Health and Human Services, United States Public Health Service, Food and Drug Administration; 1990.

331. Ellenberg JH, Hirtz DG, Nelson KB: Do seizures in children cause intellectual deterioration. N Engl J Med 1986; 314(17):1085-1088.

332. Shields WD, Nielsen C, Buch D, et al: Relationship of pertussis immunization to the onset of neurologic disorders: a retrospective epidemiologic study. J Pediatr 1988; 113(5):801-805.

101 333. Braun MM, Terracciano G, Salive ME, et al: Report of a US public health service workshop on hypotonic- hyporesponsive episode (HHE) after pertussis immunization. Pediatrics 1998; 102(5):E52.

334. Miller DC, Wadsworth MJ, Ross EM: Pertussis vaccine and severe acute neurological illnesses. Response to a recent review by members of the NCES team. Vaccine 1989; 7(6):487-489.

335. Bellman MH, Ross EM, Miller DL: Infantile spasms and pertussis immunisation. Lancet 1983; 1(8332):1031-1034.

336. Safety of pertussis vaccine. Lancet 1990; 335(8690):655-656.

337. Miller D, Madge N, Diamond J, Wadsworth J, Ross E: Pertussis immunisation and serious acute neurological illnesses in children. BMJ 1993; 307(6913):1171-1176.

338. Griffith AH: Pertussis vaccines and permanent brain damage. Vaccine 1989; 7(6):489-490.

339. Bowie C: Lessons from the pertussis vaccine court trial. Lancet 1990; 335(8686):397-399.

340. Stephenson JB: A neurologist looks at neurological disease temporally related to DTP immunization. Tokai J Exp Clin Med 1988; 13(Suppl):157-164.

341. Leviton A: Neurologic sequelae of pertussis immunization–1989. J Child Neurol 1989; 4(4):311-314.

342. Riikonen R, Donner M. Incidence and aetiology of infantile spasms from 1960 to 1976: a population study in Finland. Dev Med Child Neurol 21(3):333–343, 1979.

343. Riikonen R, Donner M: Incidence and aetiology of infantile spasms from 1960 to 1976: a population study in Finland. Dev Med Child Neurol 1979; 21(3):333-343.

344. Millichap JG: Etiology and treatment of infantile spasms: current concepts, including the role of DPT immunization. Acta Paediatr Jpn 1987; 29(1):54-60.

345. Melchior JC: Infantile spasms and early immunization against whooping cough. Danish survey from 1970 to 1975. Arch Dis Child 1977; 52(2):134-137.

346. Fukuyama Y, Tomori N, Sugitate M: Critical evaluation of the role of immunization as an etiological factor of infantile spasms. Neuropadiatrie 1977; 8(3):224-237.

347. Lombroso CT: A prospective study of infantile spasms: clinical and therapeutic correlations. Epilepsia 1983; 24(2):135- 158.

348. Guyer B, Martin JA, MacDorman MF, et al: Annual summary of vital statistics—1996. Pediatrics 1997; 100(6):905-918.

349. Bernier RH, Frank Jr JA, Dondero Jr TJ, Turner P: Diphtheria-tetanus toxoids-pertussis vaccination and sudden infant deaths in Tennessee. J Pediatr 1982; 101(3):419-421.

350. Baraff LJ, Ablon WJ, Weiss RC: Possible temporal association between diphtheria-tetanus toxoid-pertussis vaccination and sudden infant death syndrome. Pediatr Infect Dis 1983; 2(1):7-11.

351. Torch W: Diphtheria-pertussis-tetanus (DPT) immunization: a potential cause of sudden infant death syndrome (SIDS). J Pediatr 1982; 101:169-170.

352. Torch W: Characteristics of diphtheria-pertussis-tetanus (DPT) postvaccinal deaths and DPT-caused suddent infant death syndrome (SIDS): a review. Neurology 1986; 36(suppl 1):148.

353. Nickerson B, Robison B: How many sudden infant death syndrome victims were recently immunized?. Western Soc Pediatr Res Clin Res 1985; 33:121A.

354. Taylor EM, Emergy JL: Immunization and cot deaths. Lancet 1982; 2(8300):721.

102 355. Hoffman HJ, Hunter JC, Damus K, et al: Diphtheria-tetanus-pertussis immunization and sudden infant death: results of the National Institute of Child Health and Human Development Cooperative Epidemiological Study of Sudden Infant Death Syndrome risk factors. Pediatrics 1987; 79(4):598-611.

356. Bouvier-Colle MH, Flahaut A, Messiah A, et al: Sudden infant death and immunization: an extensive epidemiological approach to the problem in France—winter 1986. Int J Epidemiol 1989; 18(1):121-126.

357. Griffin MR, Ray WA, Livengood JR, Schaffner W: Risk of sudden infant death syndrome after immunization with the diphtheria-tetanus-pertussis vaccine. N Engl J Med 1988; 319(10):618-623.

358. Geraghty K, Presentation to the Immunization Practices Advisory Committee, Centers for Disease Control; October 25, 1985; Atlanta, GA.

359. Walker AM, Jick H, Perera DR, et al: Diphtheria-tetanus-pertussis immunization and sudden infant death syndrome. Am J Public Health 1987; 77(8):945-951.

360. Solberg DTP immunization, visit to child health center and sudden infant death syndrome (SIDS). Paper presented at: Oslo Health Council, 1985; Norway.

361. Wennergren G, Milerad J, Lagercrantz H, et al: The epidemiology of sudden infant death syndrome and attacks of lifelessness in Sweden. Acta Paediatr Scand 1987; 76(6):898-906.

362. Howson CP, Fineberg HV: The ricochet of magic bullets: summary of the Institute of Medicine Report, Adverse Effects of Pertussis and Rubella Vaccines. Pediatrics 1992; 89(2):318-324.

363. Skowronski DM, De Serres G, MacDonald D, et al: The changing age and seasonal profile of pertussis in Canada. J Infect Dis 2002; 185(10):1448-1453.

364. Ridgway D: Disputed claims for pertussis vaccine injuries under the National Vaccine Injury Compensation Program. J Investig Med 1998; 46(4):168-174.

365. Mills KH, Barnard A, Watkins J, Redhead K: Cell-mediated immunity to Bordetella pertussis: role of Th1 cells in bacterial clearance in a murine respiratory infection model. Infect Immun 1993; 61(2):399-410.

366. Petersen JW, Andersen P, Ibsen PH, et al: Proliferative responses to purified and fractionated Bordetella pertussis antigens in mice immunized with whole-cell pertussis vaccine. Vaccine 1993; 11(4):463-472.

367. Petersen JW, Ibsen PH, Haslov K, Heron I: Proliferative responses and gamma interferon and tumor necrosis factor production by lymphocytes isolated from tracheobroncheal lymph nodes and spleen of mice aerosol infected with Bordetella pertussis. Infect Immun 1992; 60(11):4563-4570.

368. Redhead K, Watkins J, Barnard A, Mills KH: Effective immunization against Bordetella pertussis respiratory infection in mice is dependent on induction of cell-mediated immunity. Infect Immun 1993; 61(8):3190-3198.

369. Adamson PC, Wu TC, Meade BD, et al: Pertussis in a previously immunized child with human immunodeficiency virus infection. J Pediatr 1989; 115(4):589-592.

370. Bromberg K, Tannis G, Steiner P: Detection of Bordetella pertussis associated with the alveolar macrophages of children with human immunodeficiency virus infection. Infect Immun 1991; 59(12):4715-4719.

371. Mills KH, Ryan M, Ryan E, Mahon BP: A murine model in which protection correlates with pertussis vaccine efficacy in children reveals complementary roles for humoral and cell-mediated immunity in protection against Bordetella pertussis. Infect Immun 1998; 66(2):594-602.

372. Gearing AJ, Bird CR, Redhead K, Thomas M: Human cellular immune responses to Bordetella pertussis infection. FEMS Microbiol Immunol 1989; 1(4):205-211.

373. De Magistris MT, Romano M, Nuti S, et al: Dissecting human T cell responses against Bordetella species. J Exp Med 1988; 168(4):1351-1362.

103 374. Peppoloni S, Nencioni L, Di Tommaso A, et al: Lymphokine secretion and cytotoxic activity of human CD4+ T-cell clones against Bordetella pertussis. Infect Immun 1991; 59(10):3768-3773.

375. Petersen JW, Ibsen PH, Bentzon MW, et al: The cell mediated and humoral immune response to vaccination with acellular and whole cell pertussis vaccine in adult humans. FEMS Microbiol Immunol 1991; 3(5):279-287.

376. Podda A, Nencioni L, De Magistris MT, et al: Metabolic, humoral, and cellular responses in adult volunteers immunized with the genetically inactivated pertussis toxin mutant PT-9K/129G. J Exp Med 1990; 172(3):861-868.

376a. Meyer CU, Zepp F, Decker M, Lee M, Chang SJ, Ward J, Yoder S, Bogaert H, Edwards KM: Cellular immunity in adolescents and adults following acellular pertussis vaccine administration. Clin Vaccine Immunol 2007 Mar; 14(3):288- 292.Epub 2007 Jan 31.

377. Zepp F, Knuf M, Habermehl P, et al: Pertussis-specific cell-mediated immunity in infants after vaccination with a tricomponent acellular pertussis vaccine. Infect Immun 1996; 64(10):4078-4084.

377a. Guiso N, Njamkepo E, Vié le Sage F, Zepp F, Meyer CU, Abitbol V, Clyti N, Chevallier S: Long-term humoral and cell- mediated immunity after acellular pertussis vaccination compares favourably with whole-cell vaccines 6 years after booster vaccination in the second year of life. Vaccine 2007 Feb 9; 25(8):1390-1397.Epub 2006 Nov 7

378. Ausiello CM, Lande R, Urbani F, et al: Cell-mediated immunity and antibody responses to Bordetella pertussis antigens in children with a history of pertussis infection and in recipients of an acellular pertussis vaccine. J Infect Dis 2000; 181(6):1989-1995.

379. Ausiello CM, Lande R, Urbani F, et al: Cell-mediated immune responses in four-year-old children after primary immunization with acellular pertussis vaccines. Infect Immun 1999; 67(8):4064-4071.

380. Cassone A, Ausiello CM, Urbani F: Cell-mediated and antibody responses to Bordetella pertussis antigens in children vaccinated with acellular or whole-cell pertussi vaccines. Arch Pediatr Adolesc Med 1997; 151:282-289.

381. Cassone A, Mastrantonio P, Ausiello CM: Are only antibody levels involved in the protection against pertussis in acellular pertussis vaccine recipients. J Infect Dis 2000; 182(5):1575-1577.

382. Tran Minh NN, He Q, Edelman K, et al: Cell-mediated immune responses to antigens of Bordetella pertussis and protection against pertussis in school children. Pediatr Infect Dis J 1999; 18(4):366-370.

383. Edelman KJ, He Q, Makinen JP, et al: Pertussis-specific cell-mediated and humoral immunity in adolescents 3 years after booster immunization with acellular pertussis vaccine. Clin Infect Dis 2004; 39(2):179-185.

384. Miller JJ SR, Saito TM: An agglutinative reaction for Haemophilus pertussis, II: its relations to clincial immunity. J Pediatr 1943; 22:644-651.

385. Olin P, Hallander HO, Gustafsson L, et al: How to make sense of pertussis immunogenicity data. Clin Infect Dis 2001; 33(Suppl 4):S288-S291.

386. Cherry JD, Gornbein J, Heininger U, Stehr K: A search for serologic correlates of immunity to Bordetella pertussis cough illnesses. Vaccine 1998; 16(20):1901-1906.

387. Hewlett EL, Halperin SA: Serological correlates of immunity to Bordetella pertussis. Vaccine 1998; 16(20):1899-1900.

388. Poland GA: Still more questions on pertussis vaccines. Lancet 1997; 350(9091):1564-1565.

389. Pertussis vaccination acellular pertussis vaccine for reinforcing and booster use—supplementary ACIP statement. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR Recomm Rep 1992; 41(RR-1):1-10.

390. Storsaeter J, Olin P, Renemar B, et al: Mortality and morbidity from invasive bacterial infections during a clinical trial of acellular pertussis vaccines in Sweden. Pediatr Infect Dis J 1988; 7(9):637-645.

391. Isomura S: License application for pertussis vaccine withdrawn in Sweden. Lancet 1989;I:114. Lancet 1989; 1:114.

104 392. Samore MH, Siber GR: Effect of pertussis toxin on susceptibility of infant rats to Haemophilus influenzae type b. J Infect Dis 1992; 165(5):945-948.

393. Black SB, Cherry JD, Shinefield HR, et al: Apparent decreased risk of invasive bacterial disease after heterologous childhood immunization. Am J Dis Child 1991; 145(7):746-749.

394. Davidson M, Letson GW, Ward JI, et al: DTP immunization and susceptibility to infectious diseases. Is there a relationship. Am J Dis Child 1991; 145(7):750-754.

395. Joffe LS, Glode MP, Gutierrez MK, et al: Diphtheria-tetanus toxoids-pertussis vaccination does not increase the risk of hospitalization with an infectious illness. Pediatr Infect Dis J 1992; 11(9):730-735.

396. Kimura M, Kuno-Sakai H: Acellular pertussis vaccines and fatal infections. Lancet 1988; 1(8590):881-882.

397. Blackwelder WC, Storsaeter J, Olin P, Hallander HO: Acellular pertussis vaccines. Efficacy and evaluation of clinical case definitions. Am J Dis Child 1991; 145(11):1285-1289.

398. Storsaeter J, Hallander H, Farrington CP, et al: Secondary analyses of the efficacy of two acellular pertussis vaccines evaluated in a Swedish phase III trial. Vaccine 1990; 8(5):457-461.

399. Olin P, Storsaeter J. Vaccine efficacy. In a Clinical Trial of Accellular Pertussis Vaccines in Sweden, Techinical Report. Paper presented at: National Bacteriological Laboratory, 1988; Stockholm, Sweden.

400. World Health Organistion WHO Meeting on Case Definition of Pertussis. Paper presented at: Who Meeting on Case Definition of Pertussis; January 10–11, 1991; Geneva WHO, 1:4–5.

401. Gustafsson L, Hallander H, Olin P. Efficacy Trial of Acellular Pertussis Vaccines: Techinical Report Trial I, with Results of Preplanned Analysis of Safety, Efficacy and Immunogenicity. Paper presented at: Swedish Institute for Infectious Diseases Control, 1995; Stockholm, Sweden.

402. Hallander HO, Storsaeter J, Mollby R: Evaluation of serology and nasopharyngeal cultures for diagnosis of pertussis in a vaccine efficacy trial. J Infect Dis 1991; 163(5):1046-1054.

403. Taranger J, Trollfors B, Lagergard T, et al: Unchanged efficacy of a pertussis toxoid vaccine throughout the two years after the third vaccination of infants. Pediatr Infect Dis J 1997; 16(2):180-184.

404. Heininger U, Cherry JD, Eckhardt T, et al: Clinical and laboratory diagnosis of pertussis in the regions of a large vaccine efficacy trial in Germany. Pediatr Infect Dis J 1993; 12(6):504-509.

405. Edwards KM, Decker MD: Comparison of serological results in the NIAID Multicenter Acellular Pertussis Trial with recent efficacy trials. Dev Biol Stand 1997; 89:265-273.

406. Salmaso S, Anemona A, Mastrantonio P, et al: Long-term efficacy of pertussis vaccines in Italy. PROPER Study Working Group. Dev Biol Stand 1998; 95:189-194.

407. Salmaso S, Mastrantonio P, Tozzi AE, et al: Sustained efficacy during the first 6 years of life of 3-component acellular pertussis vaccines administered in infancy: the Italian experience. Pediatrics 2001; 108(5):E81.

408. Olin P, Rasmussen F, Gustafsson L, et al: Randomised controlled trial of two-component, three-component, and five- component acellular pertussis vaccines compared with whole-cell pertussis vaccine. Ad Hoc Group for the Study of Pertussis Vaccines. Lancet 1997; 350(9091):1569-1577.

409. Plotkin SA, Cadoz M: Acellular vaccine efficacy trials. Pediatr Infect Dis J 1997; 16(9):913-914.

410. Trollfors B, Taranger J, Lagergard T, et al: A placebo-controlled trial of a pertussis-toxoid vaccine. N Engl J Med 1995; 333(16):1045-1050.

411. Trollfors B, Taranger J, Lagergard T, et al: Efficacy of a monocomponent pertussis toxoid vaccine after household exposure to pertussis. J Pediatr 1997; 130(4):532-536.

105 412. Taranger J, Trollfors B, Bergfors E, et al: Mass vaccination of children with pertussis toxoid–decreased incidence in both vaccinated and nonvaccinated persons. Clin Infect Dis 2001; 33(7):1004-1010.

413. Heininger U, Cherry JD, Stehr K, et al: Comparative Efficacy of the Lederle/Takeda acellular pertussis component DTP (DTaP) vaccine and Lederle whole-cell component DTP vaccine in German children after household exposure. Pertussis Vaccine Study Group. Pediatrics 1998; 102(3 Pt 1):546-553.

414. Cherry JD, Heininger U, Stehr K, Christenson P: The effect of investigator compliance (observer bias) on calculated efficacy in a pertussis vaccine trial. Pediatrics 1998; 102(4 Pt 1):909-912.

415. Lugauer S, Heininger U, Cherry JD, Stehr K: Long-term clinical effectiveness of an acellular pertussis component vaccine and a whole cell pertussis component vaccine. Eur J Pediatr 2002; 161(3):142-146.

416. Simondon F: Senegal pertussis trial. Dev Biol Stand 1997; 89:63-66.

417. Plotkin SA, Cadoz M: The acellular pertussis vaccine trials: an interpretation. Pediatr Infect Dis J 1997; 16(5):508-517; discussion 517–509.

418. Cherry JD: Comparative efficacy of acellular pertussis vaccines:an analysis of recent trials. Pediatr Infect Dis J 1997; 16(4 suppl):S90-S96.

419. Gustafsson L, Hallander H, Olin P. Pertussis Surveillance in Sweden: progress report Oct 1997–september 2004 with executive summary. Seven year report: Swedish Institute for Infectious Disease Contrl (SMI); June 16, 2005.

420. Olin P, Gustafsson L, Rasmussen F. Efficacy Trial of Acellular Pertussis Vaccines: Technical Report Trial II, with Results of Preplanned Analysis of Efficacy and Immunogenicity and Safety, 1997. Stockholm, Sweden: 1997.

421. Gustafsson L, Hessel L, Storsaeter J, Olin P: Long-term follow-up of Swedish children vaccinated with acellular pertussis vaccines at 3, 5, and 12 months of age indicates the need for a booster dose at 5 to 7 years of age. Pediatrics 2006; 118(3):978-984.

422. Kimura M, Kuno-Sakai H: Pertussis vaccines in Japan. Acta Paediatr Jpn 1988; 30(2):143-153.

423. Kimura M, Kuno-Sakai H: Epidemiology of pertussis in Japan. Tokai J Exp Clin Med 1988; 13(Suppl:1–7):

424. Sato Y, Sato H: Further characterization of Japanese acellular pertussis vaccine prepared in 1988 by 6 Japanese manufacturers. Tokai J Exp Clin Med 1988; 13(Suppl):79-88.

425. Ginnaga A, Morokuma K, Aihara K, et al: Characterization and clinical study on the acellular pertussis vaccine produced by a combination of column purified pertussis toxin and filamentous hemagglutinin. Tokai J Exp Clin Med 1988; 13(Suppl):59-69.

426. Kimura M, Kuno-Sakai H: Developments in pertussis immunisation in Japan. Lancet 1990; 336(8706):30-32.

427. Pittman M: History of the development of pertussis vaccine. Dev Biol Stand 1991; 73:13-29.

428. Aoyama T, Murase Y, Kato M, et al: Efficacy and immunogenicity of acellular pertussis vaccine by manufacturer and patient age. Am J Dis Child 1989; 143(6):655-659.

429. Isomura S, Suzuki S, Sato Y: Clinical efficacy of the Japanese acellular pertussis vaccine after intrafamiliar exposure to pertussis patients. Dev Biol Stand 1985; 61:531-537.

430. Mortimer Jr EA, Kimura M, Cherry JD, et al: Protective efficacy of the Takeda acellular pertussis vaccine combined with diphtheria and tetanus toxoids following household exposure of Japanese children. Am J Dis Child 1990; 144(8):899-904.

431. Cherry JD, Mortimer EA, Hackell JG, Scott JV: Clinical trials in the United States and Japan with the Lederle-Takeda and Takeda acellular pertussis-diphtheria-tetanus (APDT) vaccines. The Multicenter APDT Vaccine Study Groups. Dev Biol Stand 1991; 73:51-58.

106 432. Kuno-Sakai H, Kimura M, Ozaki K, et al: Japanese clinical trials with Takeda acellular pertussis vaccine. Tokai J Exp Clin Med 1988; 13(Suppl):15-19.

433. Morgan CM, Blumberg DA, Cherry JD, et al: Comparison of acellular and whole-cell pertussis-component DTP vaccines. A multicenter double-blind study in 4- to 6-year-old children. Am J Dis Child 1990; 144(1):41-45.

434. Glode M, Joffe L, Reisinger K, et al: Safety and immunogenicity of acellular pertussis vaccine combined with diphtheria and tetanus toxoids in 17- to 24-month-old children. Pediatr Infect Dis J 1992; 11(7):530-535.

435. Blumberg DA, Mink CM, Cherry JD, et al: Comparison of an acellular pertussis-component diphtheria-tetanus-pertussis (DTP) vaccine with a whole-cell pertussis-component DTP vaccine in 17- to 24-month-old children, with measurement of 69- kilodalton outer membrane protein antibody. J Pediatr 1990; 117(1 Pt 1):46-51.

436. Kamiya H, Nii R, Matsuda T, et al: Immunogenicity and reactogenicity of Takeda acellular pertussis-component diphtheria-tetanus-pertussis vaccine in 2- and 3-month-old children in Japan. Am J Dis Child 1992; 146(10):1141-1147.

437. Blumberg DA, Mink CM, Cherry JD, et al: Comparison of acellular and whole-cell pertussis-component diphtheria- tetanus-pertussis vaccines in infants. The APDT Vaccine Study Group. J Pediatr 1991; 119(2):194-204.

438. Watson B, Cawein A, McKee BL, Hackell JG: Safety and immunogenicity of acellular pertussis vaccine, combined with diphtheria and tetanus as the Japanese commercial Takeda vaccine, compared with the Takeda acellular pertussis component combined with Lederle's diphtheria and tetanus toxoids in two-, four- and six-month-old infants. Pediatr Infect Dis J 1992; 11(11):930-935.

439. Pertussis vaccination acellular pertussis vaccine for the forth & fifth doses of the DTP series:update to supplementary. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1992; 41(RR-15):1-5.

440. Juretzko P, von Kries R, Hermann M, et al: Effectiveness of acellular pertussis vaccine assessed by hospital-based active surveillance in Germany. Clin Infect Dis 2002; 35(2):162-167.

441. Edwards KM, Karzon DT: Pertussis vaccines. Pediatr Clin North Am 1990; 37(3):549-566.

442. Lewis K, Cherry JD, Holroyd HJ, et al: A double-blind study comparing an acellular pertussis-component DTP vaccine with a whole-cell pertussis-component DTP vaccine in 18-month-old children. Am J Dis Child 1986; 140(9):872-876.

443. Edwards KM, Lawrence E, Wright PF: Diphtheria, tetanus, and pertussis vaccine. A comparison of the immune response and adverse reactions to conventional and acellular pertussis components. Am J Dis Child 1986; 140(9):867-871.

444. Edwards KM, Bradley RB, Decker MD, et al: Evaluation of a new highly purified pertussis vaccine in infants and children. J Infect Dis 1989; 160(5):832-837.

445. Pichichero ME, Badgett JT, Rodgers Jr GC, et al: Acellular pertussis vaccine: immunogenicity and safety of an acellular pertussis vs. a whole cell pertussis vaccine combined with diphtheria and tetanus toxoids as a booster in 18- to 24-month old children. Pediatr Infect Dis J 1987; 6(4):352-363.

446. Anderson EL, Belshe RB, Bartram J: Differences in reactogenicity and antigenicity of acellular and standard pertussis vaccines combined with diphtheria and tetanus in infants. J Infect Dis 1988; 157(4):731-737.

447. Edwards K, Decker MD: Pertussis vaccine. In: Plotkin SA, Orenstein WA, ed. Vaccines, 4th ed.. Philadelphia, PA: W.B. Saunders; 2004.

448. Ciofi degli Atti ML, Olin P: Severe adverse events in the Italian and Stockholm I pertussis vaccine clinical trials. Dev Biol Stand 1997; 89:77-81.

449. Kuno-Sakai H, Kimura M: Epidemiology of pertussis and use of acellular pertussis vaccines in Japan. Dev Biol Stand 1997; 89:331-332.

107 450. McDermott C, Grimsrud K, Waters J. A cellular pertussis vaccine and whole cell pertussis vaccine: a comparison of reported selected advers events (abst P41). In abstracts of the Third Canadian National Conference on Immunization, Calgary (Alberta) Canada, December 1988.

451. Scheifele D, Halperin S. Marked reduction in febrile seizures and hypotonic-hyporesponsive episodes with acellular pertussis-based vaccines: results of Canada-wide survellance (abstr 31). Paper presented at the 37th Annual Meeting of the Infectious Diseases Society of America, Philadelphia, PA. November 1999.

452. Chen RT, Rastogi SC, Mullen JR, et al: The Vaccine Adverse Event Reporting System (VAERS). Vaccine 1994; 12(6):542-550.

453. Rosenthal S, Chen R, Hadler S: The safety of acellular pertussis vaccine vs whole-cell pertussis vaccine. A postmarketing assessment. Arch Pediatr Adolesc Med 1996; 150(5):457-460.

454. Braun MM, Mootrey GT, Salive ME, et al: Infant immunization with acellular pertussis vaccines in the United States: assessment of the first two years’ data from the Vaccine Adverse Event Reporting System (VAERS). Pediatrics 2000; 106(4):E51.

455. Pichichero ME, Deloria MA, Rennels MB, et al: A safety and immunogenicity comparison of 12 acellular pertussis vaccines and one whole-cell pertussis vaccine given as a fourth dose in 15- to 20-month-old children. Pediatrics 1997; 100(5):772-788.

456. Schmitt HJ, Beutel K, Schuind A, et al: Reactogenicity and immunogenicity of a booster dose of a combined diphtheria, tetanus, and tricomponent acellular pertussis vaccine at fourteen to twenty-eight months of age. J Pediatr 1997; 130(4):616- 623.

457. Rennels MB, Deloria MA, Pichichero ME, et al: Extensive swelling after booster doses of acellular pertussis-tetanus- diphtheria vaccines. Pediatrics 2000; 105(1):e12.

458. Liese JG, Stojanov S, Zink TH, et al: Safety and immunogenicity of Biken acellular pertussis vaccine in combination with diphtheria and tetanus toxoid as a fifth dose at four to six years of age. Munich Vaccine Study Group. Pediatr Infect Dis J 2001; 20(10):981-988.

459. Pichichero ME, Edwards KM, Anderson EL, et al: Safety and immunogenicity of six acellular pertussis vaccines and one whole-cell pertussis vaccine given as a fifth dose in four- to six-year-old children. Pediatrics 2000; 105(1):e11.

460. Rennels MB, Deloria MA, Pichichero ME, et al: Lack of consistent relationship between quantity of aluminum in diphtheria-tetanus-acellular pertussis vaccines and rates of extensive swelling reactions. Vaccine 2002; 20(Suppl 20):S44- S47.

461. Isomura S: Efficacy and safety of acellular pertussis vaccine in Aichi Prefecture, Japan. Pediatr Infect Dis J 1988; 7(4):258-262.

462. Blennow M, Granstrom M: Adverse reactions and serologic response to a booster dose of acellular pertussis vaccine in children immunized with acellular or whole-cell vaccine as infants. Pediatrics 1989; 84(1):62-67.

463. Diggle L, Deeks J: Effect of needle length on incidence of local reactions to routine immunisation in infants aged 4 months: randomised controlled trial. BMJ 2000; 321(7266):931-933.

464. Nagel J, Svec D, Waters T, Fireman P: IgE synthesis in man. I. Development of specific IgE antibodies after immunization with tetanus-diphtheria (Td) toxoids. J Immunol 1977; 118(1):334-341.

465. Mark A, Bjorksten B, Granstrom M: Immunoglobulin E responses to diphtheria and tetanus toxoids after booster with aluminium-adsorbed and fluid DT-vaccines. Vaccine 1995; 13(7):669-673.

466. Hedenskog S, Bjorksten B, Blennow M, et al: Immunoglobulin E response to pertussis toxin in whooping cough and after immunization with a whole-cell and an acellular pertussis vaccine. Int Arch Allergy Appl Immunol 1989; 89(2–3):156- 161.

108 467. Ausiello CM, Urbani F, la Sala A, et al: Vaccine- and antigen-dependent type 1 and type 2 cytokine induction after primary vaccination of infants with whole-cell or acellular pertussis vaccines. Infect Immun 1997; 65(6):2168-2174.

468. Scheifele DW, Halperin SA, Ferguson AC: Assessment of injection site reactions to an acellular pertussis-based combination vaccine, including novel use of skin tests with vaccine antigens. Vaccine 2001; 19(32):4720-4726.

469. Scheifele DW, Halperin SA, Ochnio JJ, et al: A modified vaccine reduces the rate of large injection site reactions to the preschool booster dose of diphtheria-tetanus-acellular pertussis vaccine: results of a randomized, controlled trial. Pediatr Infect Dis J 2005; 24(12):1059-1066.

470. Knuf M, Habermehl P, Faber J, et al: Assessment of nine candidate DTP-vaccines with reduced amount of antigen and/or without adjuvant as a fourth (booster-) dose in the second year of life. Vaccine 2006; 24(27–28):5627-5636.

471. Keitel WA, Muenz LR, Decker MD, et al: A randomized clinical trial of acellular pertussis vaccines in healthy adults: dose-response comparisons of 5 vaccines and implications for booster immunization. J Infect Dis 1999; 180(2):397-403.

472. Decker MD, Cates KL, Maida A. Safety and immunogenicity in adults and adolescents of Biocine acellular pertussis(aP) vaccine abstr 123.002. In Abstract of the 7th International Congress for Infectious Diseases, Hong Kong, June, 1996.

473. Edwards KM, Decker MD, Graham BS, et al: Adult immunization with acellular pertussis vaccine. JAMA 1993; 269(1):53-56.

474. Sekura RD, Zhang YL, Roberson R, et al: Clinical, metabolic, and antibody responses of adult volunteers to an investigational vaccine composed of pertussis toxin inactivated by hydrogen peroxide. J Pediatr 1988; 113(5):806-813.

475. Stehr K, Lugauer S, Heninger U: Immunogenicity and reactogenicity of Lederle/Takeda acellular pertussis vaccine in 185 German adults. Pediatr Res 1995; 37:189A.

476. Keitel W. Adult pertussis study results using five acellular vaccines. Acellular pertussis vaccine trials: results and impact on US public health. Paper presented at the National Institutes of Health Pertussis Conference, Washington, DC, June 3–5, 1996.

477. Forsyth KD, Campins-Marti M, Caro J, et al: New pertussis vaccination strategies beyond infancy: recommendations by the global pertussis initiative. Clin Infect Dis 2004; 39(12):1802-1809.

478. Forsyth K, Nagai M, Lepetic A, Trindade E: Pertussis immunization in the global pertussis initiative international region: recommended strategies and implementation considerations. Pediatr Infect Dis J 2005; 24(5 Suppl):S93-S97.

479. Wirsing von Konig CH, Campins-Marti M, Finn A, et al: Pertussis immunization in the global pertussis initiative European region: recommended strategies and implementation considerations. Pediatr Infect Dis J 2005; 24(5 Suppl):S87- S92.

480. Tan T, Halperin S, Cherry J, et al. Pertussis immunization in the global pertussis initiative North American region: recommended strategies and implementation considerations. Pediatr Infect Dis (5 Suppl):S83–S86, 2005.

481. Caro DGJ, Payne WE-HK, JA OB: Pertussis immunization of adolescents in the United States: an economic evaluation. Pediatr Infect Dis 2005.S75-S82.

482. Plotkin S: The global pertussis initiative: process overview. Pediatr Infect Dis 2005.S7-S9.

483. Tan Forsyth T, vK CH: Potential strategies to reduce the burden of pertussis. Pediatr Infect Dis 2005.S69-S74.

484. Plotkin S: Aims, scope and findings of the global pertussis initiative 2005; 24(5 suppl):S5-S6.

485. Caro J, Payne DGK: Economic burden of pertussis and the impact of immunization. Pediatr Infect Dis 2005; 24(suppl 5):S48-S54.

109 486. Greenberg D, von Konig CH: Heininger Health burden of pertussis in infants and children. Pediatr Infect Dis 2005; 24(5 Suppl):S39-S43.

487. LM Pichichero D, Johnson D: An adolescent and adult formulation combined tetanus, diphtheria and five-component pertussis vaccine. Vaccine 2006; 5(2):175-187.

488. Blatter Pichichero M, WA JHK: Acellular pertussis vaccine booster combined with diphtheria and tetanus toxoids for adolescents. Pediatrics 2006; 117(4):1084-1093.

489. Pichichero ME, Rennels MB, Edwards KM, et al: Combined tetanus, diphtheria, and 5-component pertussis vaccine for use in adolescents and adults. JAMA 2005; 293(24):3003-3011.

489a. Zepp F, Knuf M, Habermehl P, Mannhardt-Laakmann W, Howe B, Friedland LR: Safety of reduced-antigen-content tetanus-diphtheria-acellular pertussis vaccine in adolescents as a sixth consecutive dose of acellular pertussis-containing vaccine. J Pediatr 2006 Nov; 149(5):603-610.

490. Halperin S: How soon after a prior tetanus-diphtheria vaccination can one give adult formulation tetanus-diphtheria- acellular pertussis vaccine. Pediatr Infect Dis 2006; 25(3):195-200.

491. Ward J. Acellular pertussis vaccines in adolescents and adults [abstr 1291]. In Abstracts of the 41st Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL, December 16–19, 2001, p 520.

492. Wright SW, Edwards KM, Decker MD, Lamberth MM: Pertussis seroprevalence in emergency department staff. Ann Emerg Med 1994; 24(3):413-417.

492a. Halperin SA: The control of pertussis—2007 and beyond. N Engl J Med 2007 Jan 11; 356(2):110-113.

492b. Halperin SA: Recommendation for an adolescent dose of tetanus and diphtheria toxoids and acellular pertussis vaccine: reassurance for the future. J Pediatr 2006 Nov; 149(5):589-591.

493. Karen R: Broder M, Margaret M. et al. Preventing tetanus, diphtheria, and pertussis among adolescents: use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccines. MMWR 2006; 55(RR-3):1-50.

494. Preventing Tetanus Diphtheria, and Pertussis Among Adults : Use of to diagnose pertussis (66). Use of PCR tests with low specificity can result in unnecessary investigation and treatment of persons with false-positive PCR test.

www.cdc.gov/mmwr/preview/mmwrhtml/rr5517a1.htm?s_cid=rr5517a1_e

495. Canada Immunization Guide : In: Canada PPHBH, ed. 6th ed.. Ottawa, (Ontario), Canada: National Advisory Committee on Immunization; 2002.

496. Shefer A, Dales L, Nelson M, et al: Use and safety of acellular pertussis vaccine among adult hospital staff during an outbreak of pertussis. J Infect Dis 1995; 171(4):1053-1056.

497. Christie CD, Garrison KM, Kiely L, et al: A trial of acellular pertussis vaccine in hospital workers during the Cincinnati pertussis epidemic of 1993. Clin Infect Dis 2001; 33(7):997-1003.

498. Decker MD, Edwards KM: Acellular pertussis vaccines: the authors reply. N Engl J Med 1996; 334:1547-1548.

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