Flu Vaccine Effectiveness

The effectiveness of flu vaccines can vary and depends, in part, on the match between the viruses in the vaccine and the flu viruses that are circulating in the community, as well as the age and health of the person being vaccinated.
    

The influenza vaccine is used to prevent flu illness, not to treat it.
    

A flu vaccine protects against influenza. It will not protect against other respiratory viruses that may have similar symptoms to the flu.
    

It takes about two weeks after vaccination for your body to build sufficient immunity to protect against the flu.
    

Influenza vaccination can prevent illness. It can also lessen the severity of illness if you are exposed to a flu virus that is related to the flu viruses in the vaccine.
    

Some people should talk with a doctor before getting an influenza vaccine: 

• those with severe allergy to chicken eggs
• those with an allergic reaction to flu vaccines in past
• those who have ever had Guillain-Barré Syndrome (a severe paralytic illness, also called GBS)

People who have a moderate to severe illness should wait until symptoms pass to get vaccinated.
    

For more information about the seriousness of influenza and the benefits of influenza vaccination, talk to your doctor or nurse, visit www.cdc.gov/flu or call CDC at 1-800-CDC-INFO.