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Efficacy study show 92% reduction of flu risk
Influenza information from the Centers for Disease Control and Prevention (CDC) includes the following answers to common questions about the new live attenuated influenza vaccine (LAIV).
Q. How well does the LAIV work?
A. In one large study among children ages 15-85 months, LAIV reduced the chance of influenza illness by 92% compared with placebo. In a study among adults, the participants were not tested specifically for influenza. However, the study found 19% fewer severe febrile respiratory tract illnesses, 24% fewer respiratory tract illnesses with fever, 23% to 27% fever days of illness, 13% to 28% fewer lost workdays, 15% to 41% fewer health care provider visits, and 43% to 47% less use of antibiotics compared with placebo.
Q. How is LAIV different from inactivated influenza vaccine — the flu shot?
A. LAIV contains live viruses, whereas the inactivated vaccine contains killed viruses. LAIV is administered by nasal sprayer, while the inactivated vaccine is administered by needle. LAIV is approved for use only among healthy people ages 5-49 years. Inactivated influenza vaccine is approved for use among people ages > 6 months, including healthy people and those with chronic medical conditions. LAIV contains three influenza viruses, each of which represents one of the three groups of viruses circulating among people in a given year. Each of the three vaccine strains in both vaccines — one A (H3N2) virus, one A (H1N1) virus, and one B virus — are representative of the influenza vaccine strains recommended for that year. Viruses for both vaccines are grown in eggs. As is recommended for the inactivated influenza vaccine, the LAIV should be given once a year.
Q. Is one type of influenza vaccine better than the other?
A. There have been no studies large enough to compare the FluMist brand LAIV with inactivated influenza vaccine. However, studies with other live influenza vaccines and inactivated vaccine have demonstrated no difference in benefit between the two vaccines.
Q. Who can be vaccinated with LAIV?
A. LAIV is approved for use in healthy people ages 5-49 years.
Q. Who should not be vaccinated with LAIV?
A. Those who fall into the following categories:
• Children younger than 5.
• People ages > 50.
• People with a medical condition placing them at high risk for complications from influenza, including people with chronic heart or lung disease, such as asthma or reactive airways disease; people with medical conditions such as diabetes or kidney failure; or people with illnesses that weaken the immune system or who take medications that can weaken the immune system.
• Children or adolescents receiving aspirin.
• People with a history of Guillain-Barré syndrome, a rare disorder of the nervous system.
• Pregnant women.
• People with a history of allergy to any of the components of LAIV or to eggs.
Q. Should LAIV be administered to patients with chronic diseases other than those specifically listed above?
A. No. LAIV is approved for use only in healthy people ages 5-49 years.
Q. Can people receiving LAIV pass the vaccine viruses to other people?
A. In clinical studies, transmission of vaccine viruses to close contacts has occurred only rarely. The current estimated risk of getting infected with vaccine virus after close contact with a person vaccinated with LAIV is low (0.6% to 2.4%). Because the LAIV viruses are attenuated and cold-adapted, infection with LAIV is unlikely to result in influenza illness symptoms since the vaccine viruses have not been shown to mutate into typical or naturally occurring influenza viruses.
Q. Can contacts of people with weakened immune systems get LAIV?
A. Use of inactivated influenza vaccine is preferred for vaccinating household members, health care workers, and others who have close contact with people who have weakened immune systems because of the theoretical risk that a vaccine virus could be transmitted and cause illness. Otherwise, either inactivated vaccine or LAIV can be used for healthy people ages 5-49 years in close contact with other people at high risk (for example, people with heart disease who are not on medications that could weaken the immune system).