Influenza: Questions and Answers Information About the Disease and Vaccines

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Influenza: Questions and Answers information about the disease and vaccines

What causes influenza? cially older adults. Some people may also have nausea, Influenza is caused by influenza viruses. Two types of vomiting, or diarrhea; these symptoms are more often influenza, A and B, cause outbreaks in people. Both seen in children. types can cause mild to severe illness in all age groups. While influenza A viruses infect humans and other ani- How serious is influenza? mals, influenza B viruses affects only humans. Although many people think of influenza as just a com- Subtypes of type A influenza virus are identified by two mon cold, it is really a specific and serious respiratory antigenic proteins called hemagglutinin [H] and neur- infection that can result in hospitalization and death. aminidase [N] on the surface of the virus. These proteins Rates of infection from seasonal influenza are highest can change, or mutate, over time. Because these pro- among children. The risks for influenza-related compli- teins can change, people can get influenza infections cations, hospitalizations, and deaths are highest multiple times over their lifetime. An antigen “shift” among adults ages 65 years and older, children (major change) creates a new influenza A virus with a younger than 5 years, pregnant women, and people of new H, or H and N, that can cause a global epidemic if any age who have medical conditions that place them the virus can spread easily among people and if most at increased risk for complications from influenza. people do not have immunity against it. This happened From the 2010–11 through 2019–20 seasons, the most recently in 2009 when the novel H1N1 influenza annual influenza-related disease burden varied from virus appeared and led to a major pandemic. 9–49 million illnesses, 4–23 million medical visits, 140,000–960,000 hospitalizations, and 12,000–61,000 How does influenza spread? deaths per year. The number of influenza laboratory- Influenza is transmitted through the air from the respi- confirmed deaths in children reported to CDC aver- ratory tract of an infected person when they talk, aged 132 (range 37–189) per year. This is considered cough, or sneeze. It can also be transmitted by touch- an underestimate of actual pediatric deaths as some ing a surface that has respiratory droplets with influ- influenza-related deaths are likely not reported or rec- enza viruses and then touching the nose, mouth, or ognized. For more information on the health burden of possibly eyes. influenza, see www.cdc.gov/flu/about/burden/index.html. How long does it take to develop symptoms of influenza after being exposed? What are possible complications from influenza? The most frequent complication from influenza are viral The incubation period of influenza is usually two days and bacterial pneumonia. Other complications include but can range from one to four days. inflammation of the heart (myocarditis), brain (enceph- alitis) or muscle (myositis). Influenza also can worsen What are the symptoms of influenza? chronic medical conditions like cardiovascular disease, Typical influenza disease is characterized by sudden leading to heart attacks or worsening congestive heart onset of fever, aching muscles, sore throat, and non- failure, and worsening asthma and diabetes. productive cough. Additional symptoms may include Reye syndrome is a complication that occurs almost runny nose, headache, a burning sensation in the exclusively in children – patients suffer from severe chest, and eye pain and sensitivity to light. Typical vomiting and confusion, which may progress to coma influenza disease does not occur in every infected per- because of swelling of the brain. To decrease the chance son. Someone who has been previously exposed to of developing Reye syndrome, infants, children, and similar virus strains (through natural infection or vacci- teenagers should not be given aspirin for fever reduction nation) is less likely to develop serious clinical illness. or pain relief. Not everyone with influenza illness has a fever, espe-

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Saint Paul, Minnesota • 651-647-9009 • www.immunize.org • www.vaccineinformation.org www.immunize.org/catg.d/p4208.pdf • Item #P4208 (10/20) Influenza: Questions and Answers (continued) page 2 of 7

What is the best way to prevent influenza? used for both treatment and prevention (also called The best way to prevent influenza is with annual prophylaxis). It is important to remember that antiviral influenza vaccination. drugs are not a substitute for vaccination. CDC has more information on the use of influenza antiviral Is there an alternative to vaccination in preventing medications at www.cdc.gov/flu/professionals/antivirals/index.htm. influenza? No. Vaccination is the single best way to prevent influ- If I contract influenza, what should I do? enza and its complications. Some steps that may help Call your healthcare provider to discuss your particular prevent the spread of respiratory illnesses, like influ- situation. If you are at high risk of developing complica- enza, include: tions from influenza, you should consult your healthcare provider immediately if you develop influenza-like 1. Cover your nose and mouth with your sleeve or a symptoms; you may benefit from influenza antiviral tissue when you cough or sneeze – throw the tissue medicine. You will need to get plenty of rest and drink away after you use it and then wash your hands. a lot of liquids. You can also take medications to 2. Wash your hands often with soap and water, especially relieve the symptoms of influenza (but never give aspi- after you cough or sneeze. If you are not near water, rin to children or teenagers who have influenza-like use an alcohol-based hand cleaner. symptoms, particularly fever). Antiviral medicines are 3. Stay away as much as you can from people who are most beneficial when started within the first 1–2 days sick. of influenza illness. For purposes of treatment and pre- 4. If you get influenza, stay home from work or school vention, antiviral medicines are prioritized for people for at least 24 hours after the fever has ended. If you at high risk for influenza-related complications, such as are sick, don’t go near other people to avoid infect- people 65 years or older, people with chronic medical ing them. conditions, pregnant women, and young children. 5. Try not to touch your eyes, nose, or mouth. Viruses When is a person with influenza contagious? often spread this way. A person may pass virus from 1 day before symptoms Are any drugs available to prevent or treat influenza? start through 5–7 days after illness onset. There are four influenza antiviral drugs recommended Can you get influenza more than once? for use in selected patients. Oseltamivir (Tamiflu) and inhaled zanamivir (Relenza) can be used for treatment Yes. Influenza viruses change frequently and infection or prevention. Oral baloxavir (Xofluza) and intravenous with one strain does not provide protection against peramivir (Rapivab) are recommended only for treat- all strains. ment. All four provide protection against both A and B viruses. Two other antiviral medications, amantadine When did influenza vaccine first become available? and rimantadine which have activity only against influ- The first influenza vaccine in the United States became enza A viruses, are not recommended for use because available in 1945. of high levels of resistance among circulating influenza A viruses. What kind of vaccine is it? Use of antiviral medications can reduce the severity The most common influenza vaccine is made from and length of influenza illness. People with severe ill- inactivated (killed) viruses that are given as an intra- ness and people at increased risk of severe illness muscular injection. Two different influenza vaccines (e.g., people at high risk of influenza complications, (cell-culture based inactivated vaccine and recombi- such as young children, people with chronic medical nant influenza vaccine or RIV) are made without the conditions, and older adults) should be treated with use of eggs. A nasal spray influenza vaccine containing influenza antiviral medications when influenza is live viruses that have been weakened (attenuated) is suspected. also available. Influenza vaccine in the United States Antiviral medicine is also recommended for use in cer- contains either 3 or 4 strains of influenza virus. There tain outbreak situations (e.g., nursing home out- is no preference for one type of vaccine over another breaks); in such cases, antiviral medication can be for people for whom more than one recommended and age-appropriate vaccine is available. continued on the next page �

Immunization Action Coalition • Saint Paul, Minnesota • 651-647-9009 • www.immunize.org • www.vaccineinformation.org www.immunize.org/catg.d/p4208.pdf • Item #P4208 (10/20) Influenza: Questions and Answers (continued) page 3 of 7

How are the vaccines made? cine. Children age 2 years and older can receive Flu- Every year, manufacturers develop and produce vaccine Mist if they do not have contraindications to FluMist. that contains virus strains that World Health Organiza- tion and, in the U.S., the FDA and CDC believe are Who recommends the influenza vaccine? most likely to circulate during the upcoming influenza The Centers for Disease Control and Prevention, the season. Influenza vaccines contain both type A and type American Academy of Pediatrics, the American Acad- B viruses. emy of Family Physicians, the American College of Phy- For the inactivated (injectable) vaccine, the viruses sicians, the American College of Obstetricians and are inactivated (killed), purified, and packaged in vials Gynecologists, and the American College of Nurse Mid- or syringes. Live attenuated influenza virus vaccine is wives all recommend influenza vaccine. packaged in a special nasal sprayer. Recombinant tech- nology is used to make recombinant influenza vaccine; How often should this vaccine be given? this vaccine only includes one part of the influenza virus, Influenza vaccine is given each year because immunity the hemagglutinin, in the vaccine. About six months are decreases after a year and because influenza vaccine required to produce influenza vaccine each year. For viruses are updated almost every year. An annual vacci- more information about how influenza vaccines are nation is recommended even if the strains included in made, see the vaccine are not changed from one year to the next. www.cdc.gov/flu/prevent/how-fluvaccine-made.htm. When should people be vaccinated? How is the vaccine given? Vaccination is recommended to be offered by the end The inactivated and recombinant vaccines are given as of October, before influenza activity in the community an intramuscular injection. The live attenuated vaccine begins. Vaccination should continue to be offered as is sprayed into the nose. long as influenza viruses are circulating and unexpired vaccine is available. To avoid missed opportunities for Is the vaccine that contains 4 viruses preferred vaccination, providers should offer vaccination during over the vaccine that contains 3 viruses? routine healthcare visits and hospitalizations. Travelers should be aware that the influenza season typically Most influenza vaccine available in the United States occurs from April to September in the Southern Hemi- contains 4 strains of influenza virus. CDC and other sphere and throughout the year in the tropics. If they groups do not have a preference for use of the 4-virus missed vaccination in the previous season, they should vaccine over the 3-virus vaccine. still be vaccinated before they travel, even if it’s in the following spring or summer. Who should get influenza vaccine? CDC recommends that children age 6 months through Annual influenza vaccination is recommended for all 8 years that have not received two prior doses of influ- people ages 6 months and older who do not have a enza vaccine need 2 doses for the current season. They contraindication to the vaccine. should get their first dose as soon as vaccine becomes available; the second dose can be given 28 days or What are the unique features of giving influenza more after the first dose. vaccine to children compared with adults? For people that need only 1 dose, early vaccination Children ages 6 months through 8 years should receive (i.e., July and August) can result in reduced protection two doses of influenza vaccine, separated by at least 4 toward the end of the influenza season, particularly for weeks, the first time they receive this vaccine. Children older adults. who received 2 or more total doses of influenza vaccine before the most recent July 1 need only one dose for Should siblings of a person with a chronic illness the current season. Your doctor or other healthcare receive influenza vaccine even though the professional should be able to tell you if your child needs a second dose. chronically ill person has been vaccinated? Children age 6 through 35 months should receive only Yes. Vaccination is recommended for all people ages Afluria, Fluarix, FluLaval, or Fluzone inactivated vac- 6 months and older, including contacts of people with chronic illnesses. It is important to vaccinate everyone

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who may have close contact with people at increased influenza vaccination should not be deferred if the high- risk of severe influenza to better protect them from dose or adjuvanted formulation is not immediately influenza and its complications. Either inactivated, available. Standard dose or recombinant vaccine recombinant, or live virus vaccines can be used. should be given. If a patient is undergoing treatment for cancer, is Should siblings of a healthy child who is younger it safe to vaccinate her or him against influenza? than age 6 months be vaccinated? People with cancer need to be protected from influ- Yes, it is especially important that all household con- enza. Cancer patients and survivors are at higher risk tacts of children too young to be vaccinated against for complications from influenza, including hospital- influenza (i.e., younger than age 6 months) receive ization and death. They can and should receive inject- annual influenza vaccination to protect the infant from able (inactivated) influenza vaccine (not the live nasal serious infection. This is very important because these spray vaccine) even if they are being treated for cancer. infants are too young to be vaccinated and are most Here is a helpful CDC web page on cancer and influ- vulnerable to complications from influenza. enza for patients: www.cdc.gov/cancer/flu.

Why are different influenza vaccines (Fluzone High- Is it safe for pregnant women to get influenza Dose; Fluad) available for adults 65 and older? vaccine? Aging decreases the body’s ability to develop a good Yes. In fact, vaccination with the inactivated or recom- immune response after getting influenza vaccine. Vac- binant influenza vaccine is recommended for women cine manufacturers have taken two different who will be pregnant during the influenza season. approaches to improve the immune response in older Pregnant women are at increased risk for serious medi- people. For Fluzone High-Dose, a larger amount of cal complications from influenza. Studies have shown antigen in the vaccine gives older people a better that influenza vaccination of pregnant women helps pre- immune response and provides better protection vent influenza and its complications in both the mother against influenza. Data from clinical trials comparing and her newborn during the first 6 months of life. regular Fluzone to Fluzone High-Dose among people Women who are breastfeeding may be vaccinated. age 65 and older indicate that higher antibody levels occur after vaccination with Fluzone High-Dose. Com- A 2017 study suggested an increase in miscar- pared to standard Fluzone, the high-dose formulation reduced laboratory-confirmed influenza by about 24%. riage among women who received inactivated influenza vaccine, but earlier studies and a later For Fluad, the manufacturer includes an adjuvant to improve the response to the vaccine. The adjuvant is follow-up study did not find any risk of miscar- called MF59 and is an oil-in-water emulsion containing riage. Please provide details. squalene, an oil that occurs naturally in many plants and animals. Fluad is the first influenza vaccine A CDC-funded study, published in 2017, found that licensed in the U.S. that contains an adjuvant. Com- among women who had been vaccinated early in preg- pared to trivalent influenza vaccine without adjuvant, nancy with an influenza vaccine containing the pan- one study found that Fluad reduced laboratory-con- demic H1N1 (H1N1pdm09) component and who also firmed influenza by about 63%. Neither Fluzone High- had been vaccinated the prior season with a Dose nor Fluad should be given to people younger H1N1pdm09-containing influenza vaccine, there was than 65 years. an increased risk of spontaneous abortion (miscarriage) in the 28 days after vaccination. This study did Neither Fluzone High-Dose nor Fluad should be given not quantify the risk of miscarriage and did not prove to people younger than 65 years. CDC has stated no that influenza vaccine was the cause of the miscar- preference for using high-dose or adjuvanted vaccine riage. Earlier studies have not found a link between or standard-dose or recombinant influenza vaccine for influenza vaccination and miscarriage. A larger follow- people age 65 and older. But it is reasonable for a per- up study, also funded by CDC, which included 3 more son age 65 years or older to receive either Fluzone years of data found no association between early mis- High-Dose or Fluad if it is readily available. However,

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carriage and influenza vaccination, regardless of previ- tion who previously experienced GBS within 6 weeks of ous influenza season vaccination. These results are an influenza vaccination should generally not be vacci- reassuring regarding the safety of influenza vaccination nated. Instead, their physician may consider using of pregnant women. influenza antiviral drugs during the time of potential exposure to influenza. About 80 to 160 people get GBS CDC, ACIP, and the American College of Obstetricians each week in the United States, regardless of and Gynecologists (ACOG) have not changed the rec- vaccination. ommendation for influenza vaccination of pregnant women. It is recommended that pregnant women What can you tell me about the preservative receive influenza vaccine during any trimester of their thimerosal that is in some injectable influenza pregnancy because influenza poses a danger to preg- vaccines and the claim that it might be associated nant women and their infants, and the influenza vaccine prevents illness in both the mother and her infant. with the development of autism? Thimerosal is a very effective preservative that has been How safe is this vaccine? used to prevent bacterial contamination in vaccines for more than 50 years. It contains a type of mercury known Influenza vaccine is very safe. The most common side as ethylmercury. Ethylmercury is different from methyl- effects of the injectable (inactivated) influenza vaccine mercury, which is the form that is in some fish and include soreness, redness, or swelling at the site of other seafood. At very high levels, methylmercury can be the injection. These reactions are temporary and occur toxic to people, especially to the neurological develop- in 15%–20% of recipients. Less than 1% of vaccine ment of infants. recipients develop symptoms such as fever, chills, and muscle aches for 1 to 2 days following the vaccination. Several large scientific studies have determined that Experiencing these non-specific side effects does not thimerosal in vaccines does not lead to neurologic mean that you are getting influenza. problems, including autism. However, because we generally try to reduce people’s exposure to mercury if Healthy children ages 2 through 4 years who receive at all possible, vaccine manufacturers have voluntarily the nasal spray live attenuated influenza vaccine (LAIV) changed their production methods to produce vaccines during clinical trials appeared to have an increased that are now free of thimerosal or have only trace chance of wheezing. LAIV is not recommended for chil- amounts. They have done this because it is possible to dren aged 2 through 4 years who have received a diag- do, not because there was any evidence that the thi- nosis of asthma or whose parents or caregivers report merosal was harmful. For a list of which influenza vac- that a healthcare provider has told them during the cines contain thimerosal, see past 12 months that their child had wheezing or www.cdc.gov/flu/professionals/vaccines.htm. asthma or whose medical record indicates a wheezing episode occurring during the preceding 12 months. Healthy adults receiving the live influenza vaccine How effective is influenza vaccine? reported symptoms such as cough, runny nose, sore Protection from influenza vaccine varies by the similar- throat, chills, and tiredness at a rate 3%–18% higher ity of the vaccine strain(s) to the circulating strains, than for placebo recipients. and the age and health of the recipient. Healthy people younger than age 65 years are more likely to have pro- Serious adverse reactions to influenza vaccine are very tection from their influenza vaccination than are older, rare. Such reactions are most likely the result of an frail individuals. Although the vaccine is not as effec- allergy to a vaccine component. In 1976, the swine tive in preventing influenza disease among the elderly, influenza vaccine was associated with a severe illness it is effective in preventing complications, including called Guillain-Barré syndrome (GBS), a nerve condi- hospitalization, ICU admission, COPD exacerbations, tion that can result in temporary paralysis that influenza-related cardiovascular events, and death. occurred in about 1 per 100,000 persons. Injectable influenza vaccines since then have not been clearly When the “match” between vaccine and circulating linked with GBS, but if there is a risk of GBS after influ- strains is close, the injectable (inactivated) vaccine enza vaccination, it is small – on the order of about 1–2 prevents influenza in about 40%–60% of people. Among cases per million persons vaccinated. However, as a pre- elderly nursing home residents, the vaccine is most caution, any person without a high risk medical condi- effective in preventing severe illness, secondary compli-

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cations, and deaths related to influenza. CDC has sum- apy in children and adolescents because of the risk marized influenza vaccine benefits at of Reye syndrome www.cdc.gov/flu/prevent/vaccine-benefits.htm. ●●Children ages 2 through 4 years who have received Can influenza vaccine cause influenza? a diagnosis of asthma or whose parents or caregivers report that a healthcare provider has told them No. Neither the injectable (inactivated or recombinant) during the preceding 12 months that their child vaccine nor the live attenuated (nasal spray) vaccine can had wheezing or asthma or whose medical record cause influenza. The inactivated injectable influenza indicates a wheezing episode in the preceding 12 vaccine contains only killed virus fragments and the months recombinant vaccine contains only a part of the influenza virus so neither type of vaccine can cause influ- ●●Immunosuppression due to any cause, including enza. Fewer than 1% of people develop influenza-like medications or HIV infection symptoms, such as mild fever and muscle aches, after ●●Cerebral spinal fluid (CSF) leaks, cochlear implant, vaccination. These side effects are not the same as anatomic asplenia, or functional asplenia (e.g., due having the actual disease. The nasal spray influenza to sickle cell anemia) vaccine contains live attenuated (weakened) viruses ●●Close contacts and caregivers of severely immuno- that can produce mild symptoms similar to a cold. suppressed people who require a protected envi- While the viruses are able to grow in the nose and ronment (e.g., reverse isolation in a hospital) throat tissue and produce protective immunity, they ●●Pregnancy are weakened and do not grow effectively in the lung. Consequently, they cannot produce influenza disease. ●●Receipt of influenza antiviral medication before scheduled vaccination (zanamivir or oseltamivir Protective immunity develops 1 to 2 weeks after vac- within 48 hours; peramivir within 5 days; baloxavir cination. It is possible that a recently vaccinated person within 17 days) can be exposed to influenza disease before they develop immunity from the vaccine and consequently develop Precautions* to LAIV are disease. This can result in someone erroneously believ- ●●Moderate or severe acute illness with or without fever ing they developed the disease from the vaccination. ●●History of Guillain-Barre syndrome within 6 weeks of Also, to many people “the flu” is any illness with fever receipt of influenza vaccine and cold symptoms. If they get any viral illness, they ●●Asthma in a person age 5 years or older may blame it on the influenza vaccination or think they ●●Underlying medical conditions that might predispose got “the flu” despite being vaccinated. Influenza vac- to complications after influenza virus infection, such cine only protects against certain influenza viruses, not as chronic pulmonary, cardiovascular (except isolated all viruses. hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders, including diabetes mellitus Who should NOT receive influenza vaccine? *As a general rule, people with a precaution should not In general, the inactivated (injectable) influenza vaccine receive LAIV, but there may be situations when the clini- can be given to everyone except children younger than cian may decide to administer it. age 6 months and people with a history of a severe allergic reaction to a previous dose of influenza vaccine Healthcare workers, household members, and others who (see next question). The recombinant vaccine is have close contact with severely immunocompromised licensed for people 18 years and older. The live, attenu- individuals during the periods in which the immuno- ated influenza vaccine (LAIV) nasal spray is licensed suppressed person requires care in protective isolation for use only in healthy, non-pregnant individuals ages 2 should receive the injectable vaccine or RIV rather than through 49 years. LAIV. Contraindications to LAIV are People who are moderately or severely ill at the time of their influenza vaccination appointment should usually ●● History of a severe allergic reactions to a vaccine wait until their symptoms are improved before getting component (except egg, see next question) or after the vaccine. Only serious, life-threatening allergies to a previous dose of any influenza vaccine thimerosal are reasons not to be vaccinated with an ●●Concomitant aspirin- or salicylate-containing ther- influenza vaccine containing thimerosal.

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What are the recommendations for influenza by ACIP, providers may prefer administering an age- vaccination of people who have an egg allergy? appropriate egg-free vaccine (ccIIV4 or RIV4) for patients with severe egg allergy. CDC recommends that people with a history of egg allergy who have experienced only hives after exposure A previous severe allergic reaction to influenza vaccine, to egg should receive influenza vaccine without spe- regardless of the component suspected to be responsi- cific precautions (except for a 15-minute observation ble for the reaction, is a contraindication to future period for syncope). Any age-appropriate vaccine (IIV, receipt of the vaccine. For a complete list of vaccine RIV, or LAIV) may be used. components (i.e., excipients and culture media) used in the production of the vaccine, see the package insert For people who report having had an allergic reaction (available at www.immunize.org/fda) or go to more severe than hives (e.g., anaphylaxis, needing epi- www.cdc.gov/vaccines/pubs/pinkbook/downloads/ nephrine), if a vaccine other than Flucelvax Quadriva- appendices/B/excipient-table-2.pdf. lent (ccIIV4, Seqirus, licensed for people age 4 years and older), or Flublok Quadrivalent (RIV4, Sanofi Pas- For more details about giving influenza vaccine to peo- teur, licensed for age 18 years and older) is given, the ple with a history of egg allergy, see the ACIP guidance vaccine should be administered in an inpatient or out- at www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/ patient medical setting supervised by a healthcare pro- flu.html. You also may find the IAC handout “Influenza vider who is able to recognize and manage severe aller- Vaccination of People with a History of Egg Allergy” gic conditions. Although not specifically recommended helpful (see www.immunize.org/catg.d/p3094.pdf).

Immunization Action Coalition • Saint Paul, Minnesota • 651-647-9009 • www.immunize.org • www.vaccineinformation.org www.immunize.org/catg.d/p4208.pdf • Item #P4208 (10/20)