Key Facts About Flu Vaccine
October 7, 2004
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Preventing the flu: The single best way to protect against the flu is to get vaccinated each fall.
There are two types of vaccines:
- The "flu shot"—an inactivated
vaccine (containing killed virus) that is given with a
needle, usually in the arm. The flu shot is approved for
use in people older than 6 months, including healthy people
and people with chronic medical conditions. About 58 million
flu shots will be available in the United States this
season.
- The nasal-spray flu vaccine—a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for “Live Attenuated Influenza Vaccine”). LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant. About 3 million doses of LAIV will be available in the United States this season.
Each vaccine contains three influenza viruses—one A (H3N2) virus, one A (H1N1) virus, and one B virus. The viruses in the vaccine change each year based on international surveillance and scientists’ predictions about which types and strains of viruses will circulate in a given year.
About 2 weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body.
When to Get Vaccinated
October or November is the best time to get vaccinated, but you can still get vaccinated in December and later. Flu season can begin as early as October and last as late as May.
Who Should Get Vaccinated
Because of a shortfall in flu shot production for this season, CDC is recommending that certain people be given priority for getting the flu shot. People in the following groups should seek vaccination this season:
- all children aged 6–23 months;
- adults aged 65 years and older;
- persons aged 2–64 years with underlying chronic medical conditions;
- all women who will be pregnant during the influenza season;
- residents of nursing homes and long-term care facilities;
- children aged 6 months–18 years on chronic aspirin therapy;
- health-care workers involved in direct patient care; and
- out-of-home caregivers and household contacts of children aged <6 months.
These are people that are at high risk for serious flu complications or are in contact with people at high risk for serious flu complications.
If available, vaccination with LAIV is an option for healthy persons aged 5-49 years who are caregivers of children less than 6 months of age and for health-care workers. If a health-care worker receives LAIV, that worker should refrain from contact with severely immunosuppressed patients requiring care in a protected environment for 7 days after vaccination.
People who are not included in one of the priority groups listed above are asked to forego or defer vaccination because of the vaccine supply situation.
Vaccine Effectiveness
The ability of flu vaccine to protect a person depends on the age and health status of the person getting the vaccine, and the similarity or "match" between the virus strains in the vaccine and those in circulation. Testing has shown that both the flu shot and the nasal-spray vaccine are effective at preventing the flu.
Vaccine Side Effects (What to Expect)
Different side effects can be associated with the flu shot and LAIV.
The flu shot: The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. Some minor side effects that could occur are:
- Soreness, redness, or swelling where the shot was given
- Fever (low grade)
- Aches
If these problems occur, they begin soon after the shot and usually last 1 to 2 days. Almost all people who receive influenza vaccine have no serious problems from it. However, on rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions.
LAIV: The viruses in the nasal-spray vaccine are weakened and will not cause severe symptoms often associated with influenza illness. (In clinical studies, transmission of vaccine viruses to close contacts has occurred only rarely.)
In children, side effects can include:
- runny nose
- headache
- vomiting
- muscle aches
- fever
In adults, side effects can include:
- runny nose
- headache
- sore throat
- cough
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