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Questions and Answers on FluMist (Influenza Virus Vaccine Live, Intranasal)

Date: October 14, 2003
Source: Food and Drug Administration (FDA)

What is FluMist approved for?
FluMist is approved to prevent influenza illness due to influenza A and B viruses in healthy children and adolescents, ages 5-17 years, and healthy adults, ages 18-49 years.
What is the difference between live attenuated influenza virus (LAIV) and the flu shot that is made from inactivated viruses?
LAIV and inactivated influenza vaccine contain strains of influenza viruses that are matched to protect against influenza strains that are likely to circulate each year. Viruses for both vaccines are grown in eggs. Both vaccines are administered annually to provide optimal protection against influenza infection. Inactivated vaccines are produced by killing the flu viruses. The killed viruses cannot cause influenza.
LAIV contains attenuated (or weakened) viruses. These weakened strains usually do not cause illness because they have lost virulence (disease-causing properties). There is, however, a possibility that they can still reproduce and cause disease, especially in persons with weakened immune systems.
FluMist (LAIV) is administered intranasally by sprayer, whereas inactivated influenza vaccine is administered intramuscularly by injection. FluMist (LAIV) is approved for use only among healthy persons aged 5-49 years; inactivated influenza vaccine is approved for use among persons aged >6 months, including those who are healthy and those with medical conditions.
Since the flu shot is recommended for many people over the age of 49, why isn¿t FluMist recommended for individuals 50 years of age and older?
Studies with FluMist did not include enough patients over the age of 49 to determine if they respond differently than younger individuals. Therefore, the safe and effective use of FluMist in persons 50 years and older has not been established.
How many doses are recommended per season?
Children 5-8 years old need two doses at least 6 weeks apart in their first year of vaccination with FluMist.
Individuals 9-49 years old need only one dose.
How well does this vaccine work?
The vaccine prevented influenza associated illness in approximately 87% of the children included in the trial.
Adults (ages 18-49 years) who received FluMist experienced significantly fewer episodes of severe febrile illness (SFI) when compared to those who received placebo. Severe febrile illness was defined as having at least three days of symptoms (runny nose, sore throat, cough, muscle aches, tiredness/weakness) and one day of fever.
Adults who received FluMist did not experience a significant reduction in any febrile illness (AFI). Adults were characterized as having AFI if they had symptoms for at least two consecutive days, with fever on at least one day.
As with any vaccine, FluMist may not protect 100% of individuals receiving the vaccine.
What are the most common side affects of FluMist?
Nasal congestion, runny nose, sore throat, headache, irritability, decreased activity, muscle ache and cough are the most common adverse events associated with the vaccine.
Nasal congestion, runny nose, sore throat, headache, irritability, decreased activity, muscle ache and cough are the most common adverse events associated with the vaccine.
However, a vaccine, like any medicine, is capable of causing serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small, and serious problems from flu vaccine are rare.
Are there certain people who should not receive FluMist?
As with any medication, individuals should check with their health care provider before receiving any flu vaccines. According to the approved package insert, the following people should not get the intranasal influenza vaccine:
Adults 50 years of age or older, or children younger than 5 should not receive FluMist.
FluMist should not be given for any reason to people with immune suppression. This includes people with primary immune deficiency diseases, as well as people with immune deficiencies related to HIV infection, cancer, or other conditions, and people who are being treated with drugs that cause immunosuppression.
The safety of FluMist in people with asthma or other reactive airway diseases has not been established, and therefore, is not recommended for use in patients with a history of reactive airway problems.
Additionally, FluMist should not be given to people with chronic underlying medical conditions that may predispose them to severe flu infections. For these people, the injected vaccine is indicated.
Individuals with egg allergies should not receive this or any other flu vaccine.
People who have health problems associated with heart disease, kidney disease, lung disease, or metabolic diseases such as diabetes, anemia and other blood disorders should not receive FluMist.
Because Reye syndrome in children has been associated with administration of aspirin during influenza virus infections, FluMist is not recommended in children and adolescents 5-17 years of age if they are receiving aspirin or aspirin-containing therapy.
Pregnant women should not receive FluMist.
Anyone with a history of Guillain-Barré Syndrome (GBS) should not receive FluMist.
FluMist recipients should avoid close contact (e.g., within the same household) with anyone with a weakened immune system for at least 21 days after receiving the vaccine.
If I receive FluMist, is it possible that I will get the flu from the vaccine?
Vaccination with FluMist involves the administration of attenuated (weakened) viruses into the nose by a sprayer. Some recipients experience low-grade fever, upper respiratory symptoms and muscle aches, but these are generally milder than when a person has a symptomatic influenza infection. Although the vaccine viruses are attenuated in healthy people, there is little information regarding the use of FluMist in people with weakened or compromised immune systems. Therefore, people with weakened or compromised immune systems should not receive FluMist.
Can I get the flu from the inactivated vaccine?
No. Components in the inactivated influenza vaccine are made from killed influenza viruses, and they cannot cause influenza infection.
Does FluMist contain thimerosal?
FluMist, which is filled into individual single-dose sprayers, does not contain thimerosal, nor is thimerosal used at any point in manufacturing FluMist. Thimerosal, which prevents the growth of microorganisms such as bacteria or fungi, is used as a preservative for inactivated influenza vaccines in multidose containers. Preservative-free inactivated influenza vaccines are also available.
What is the best time of year to receive the flu vaccine?
Flu vaccines should be administered prior to exposure to influenza. The peak of influenza activity varies from year to year, but generally occurs in the U.S. between late December and early March. Influenza vaccines usually become available in early October, but contact your healthcare provider for additional information.
Will I need to receive a vaccine every year?
Because yearly variation in the influenza strains is possible, annual revaccination with FluMist, as well as with the inactivated vaccine, is recommended.
If I would like to obtain additional information where can I find it?
We recommend that that you talk to your health care provider when you have any questions related to the medication(s) you receive. He or she can also suggest other sources of information.
Call your local or state health department.
Contact the Centers for Disease Control and Prevention (CDC): Call 1-800-232-2522 (English) Call 1-800-232-0233 (Español) Visit CDC websites at or
A copy of the vaccine package insert is available on CBER's web site at: