Evaluation of the Impact of a Pertussis Cocooning Program on Infant Pertussis Infection
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ORIGINAL STUDIES Evaluation of the Impact of a Pertussis Cocooning Program on Infant Pertussis Infection C. Mary Healy, MD,*†‡ Marcia A. Rench, BSN,* Susan H. Wootton, MD,§ and Luis A. Castagnini, MD*† (DTaP) vaccine, the United States recorded its highest number of Background: Tetanus, diphtheria and acellular pertussis immunization of pertussis cases (48,277) in over 50 years in 2012.5 Infants who are infant contacts (cocooning) is recommended by the Centers for Disease too young to have received their primary immunization series at 2, Control and Prevention to prevent infant pertussis. We determined whether 4 and 6 months of age consistently have the highest pertussis attack implementing a cocooning program at Ben Taub General Hospital, Hou- rates and complications. Pertussis-related deaths occur predomi- ston, reduced severe pertussis in young infants. nantly in infants less than 3 months of age.5–8 Reducing pertussis Methods: Infants ≤6 months of age, diagnosed with pertussis (determined disease burden in young infants has been the objective of pertussis by International Classification of Diseases, Ninth Revision codes and immunization recommendations from the Centers for Disease Con- microbiology records) at 4 hospitals, and born at times when only postpar- trol and Prevention (CDC) since the tetanus, diphtheria and acel- tum women (January 2008 through May 2009) and all infant contacts (June 2009 through August 2011) were offered tetanus, diphtheria and acellular lular pertussis (Tdap) booster vaccine for adolescents and adults pertussis vaccine at Ben Taub General Hospital were compared with infants was licensed in 2005. born preintervention (May 2004 through December 2007). Targeted immunization of postpartum women and contacts of infants under 1 year of age (cocooning) was first recommended Results: One hundred ninety-six (49%) infants with pertussis were born 9 preintervention, 140 (35%) during maternal postpartum (PP) and 64 (16%) in 2006. This recommendation was based on studies demonstrat- during cocooning (C) periods. Infants were similar in age at diagnosis (81.2 ing that most pertussis-infected infants are infected by a household contact (75%), most commonly (33%) their mother, many of whom vs. 71.3 [PP] vs. 72.5 [C] days; P 0.07), sex (male 59% vs. 51% [PP] vs. 10–12 48% [C]; P 0.17), hospitalization (68% vs. 71% [PP] vs. 78% [C]; P 0.27) are unaware that they are infected. Although data were lacking and outcome (2 deaths in the PP period; P 0.15), but more were admitted as to the efficacy of this intervention, computer simulation modeling predicted that cocooning could reduce pertussis incidence by 70% to intensive care units during cocooning (24% vs. 35% [PP] vs. 68% [C]; 13 P < 0.001). Similar proportions of infants were born at Ben Taub General in infants less than 3 months of age. Successful cocooning pro- grams in hospital, neonatal intensive care unit and pediatric clinic Hospital throughout the study (8% vs. 9% [PP] vs. 5% [C]; P 0.53). 14–16 Conclusions: Postpartum immunization and cocooning did not reduce per- settings have been reported but logistical and financial barriers precluded widespread implementation of cocooning at a national tussis illness in infants ≤6 months of age. Efforts should be directed toward 3 increasing tetanus, diphtheria and acellular pertussis immunization during level. In 2008, a pertussis immunization program was established pregnancy, combined with cocooning, to reduce life-threatening young in a county hospital in Houston, TX. Initially, the program pro- 17 infant pertussis. vided free Tdap to postpartum women, and it later expanded to include all household contacts of newborn infants (cocooning).15 Key Words: pertussis, cocooning, tetanus, diphtheria and acellular pertus- We previously reported that immunizing only postpartum women sis, infant infection with Tdap did not reduce pertussis among infants ≤6 months of age.18 The objective of the current study was to evaluate whether (Pediatr Infect Dis J 2015;34:22–26) expanding access to free Tdap vaccine to other contacts of young infants reduced severe pertussis in infants in the greater Houston metropolitan area. This study preceded the CDC recommendation onsiderable advances have been made in reducing the inci- to provide Tdap vaccine to pregnant women after week 20 of gesta- dence, morbidity and mortality of vaccine-preventable dis- tion,19 and the later recommendation that pregnant women receive C 3 eases, especially in resource-rich nations.1,2 Pertussis is an exception Tdap during the third trimester of every pregnancy. and outbreaks are regularly reported with morbidity and mortal- ity overrepresented in very young infants.3,4 Despite high infant MATERIALS AND METHODS immunization rates with diphtheria, tetanus and acellular pertussis Patient Population Infants with birth dates between May 1, 2004 and August Accepted for publication June 28, 2014. 31, 2011 and diagnosed with pertussis at ≤6 months of age at 4 From the *Department of Pediatrics, Baylor College of Medicine; †Ben Taub General Hospital; ‡Center for Vaccine Awareness and Research, Texas Chil- hospitals in the Texas Medical Center in Houston, TX [Texas Chil- dren’s Hospital; and §University of Texas Health Sciences Center at Hous- dren’s Hospital, Children’s Memorial Hermann Hospital and 2 Har- ton, Houston, TX. ris Health System county hospitals, Ben Taub General Hospital This work was supported by a research grant from Sanofi Pasteur, Inc. The Ben (BTGH) and Lyndon B. Johnson Hospital] were included in the Taub General Hospital cocooning program was supported through grants from the Baylor-Methodist Community Health Fund and the Harris County study. The majority of severe pertussis cases in young infants in Hospital District Foundations and through donated Tdap vaccine from Sanofi the Houston metropolitan area, and a substantial number of cases Pasteur. in infants who do not need hospitalization, are diagnosed in these C.M.H. is the recipient of research grants from Sanofi Pasteur and Novartis Vac- hospitals, most at Texas Children’s Hospital, which is the largest cines and serves on an Advisory Board for Novartis Vaccines and Pfizer Inc. L.A.C. is on a Speaker’s Bureau for Sanofi Pasteur. All other authors have no free-standing pediatric hospital in the United States. These infant conflicts to disclose. All authors have approved the final article. birth dates coincided with a 44-month period when pertussis immu- Address for correspondence: C. Mary Healy, MD, 1102 Bates Street, Suite 1120, nization interventions were being offered at BTGH (postinterven- Houston, TX 77030. E-mail: [email protected]. tion; January 2008 through August 2011) and compared it with a Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 0891-3668/15/3401-0022 44-month preintervention period (May 2004 through December DOI: 10.1097/INF.0000000000000486 2007). The postintervention immunization period further consisted 22 | www.pidj.com The Pediatric Infectious Disease Journal • Volume 34, Number 1, January 2015 The Pediatric Infectious Disease Journal • Volume 34, Number 1, January 2015 Cocooning and Pertussis of 2 phases, phase 1 when Tdap vaccine was offered to postpar- the preintervention period were compared first with infants diag- tum women only at BTGH (January 2008 through May 2009) and nosed in the entire postintervention period, and then infants born phase 2 when Tdap was offered to postpartum women and all infant during the preintervention, postpartum and family cocooning peri- contacts (June 2009 through August 2011), and ended when the ods were compared. Where possible, the completeness of an indi- recommendation to immunize pregnant women was posted on the vidual infant’s cocoon was calculated by assessing the proportion CDC website in August 2011. The study was approved by the insti- of their contacts who were vaccinated. The proportions of infants tutional review boards of participating hospitals and institutions. born at BTGH during different intervention periods were com- pared. Multiple logistic regression analysis accounted for potential Pertussis Diagnosis demographic confounders such as age, sex and Hispanic ethnicity. Infants with a diagnosis of pertussis were identified from 2 sources: those with a primary or secondary diagnosis of pertus- RESULTS sis using International Classification of Diseases, Ninth Revision codes (033.0, 033.1, 033.8, 033.9 and 484.3) and those identified Patient Population through microbiology laboratory records. Laboratory diagnosis was Four hundred eight infants ≤6 months of age with a birth defined as the detection of Bordetella pertussis by culture, direct date during the 88-month study period were identified as possible fluorescence assay or polymerase chain reaction (PCR). PCR was pertussis cases. Eight cases were excluded after review of the elec- performed using standard techniques to amplify the IS481 insertion tronic medical record because only B. parapertussis was identified sequence in B. pertussis (GenBank accession no. M28220), and the leaving 400 infants meeting criteria for analysis, 196 in the pre- same methods and reagents from Roche Diagnostics (Indianapolis, intervention period and 204 postintervention (Table 1). Between IN) were used in each of the hospitals. the preintervention and postintervention periods, cases of pertussis in infants ≤6 months of age increased by 70% in counties served Intervention Hospital by study hospitals. The mean age at pertussis diagnosis was 76.5 The BTGH pertussis immunization program has been pre- days (median 68) with a range of 14–207 days; 292 (73%) were <3 viously described.15,17 Briefly, free Tdap vaccine was provided to months of age. Two hundred eighteen (54.5%) infants were male postpartum women through a standing-order protocol and later to and the majority (270 [67.5%]) were of Hispanic ethnicity. Three other infant contacts. BTGH is 1 of 2 tax-supported hospitals in the hundred thirty-nine (84.8%) infants were diagnosed at Texas Chil- Harris Health System and serves a largely underinsured, medically dren’s Hospital, the only free-standing children’s hospital. Microbi- underserved population.