About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Flu vaccines will not protect against flu-like illnesses caused by non-influenza viruses.
When to Get Vaccinated
October or November is the best time to get vaccinated, but getting vaccinated in December or even later can still be beneficial since most influenza activity occurs in January or later in most years. Though it varies, flu season can last as late as May.
Who Should Get Vaccinated?
In general, those who want to reduce their chances of getting the flu can get vaccinated. However, certain people should get vaccinated each year either because they are at high risk of having serious flu-related complications or because they live with or care for high risk persons. During flu seasons when vaccine supplies are limited or delayed, the Advisory Committee on Immunization Practices (ACIP) makes recommendations regarding priority groups for vaccination.
Those people who should get vaccinated each year are:
1. People at high risk for complications from the flu, including:
- Children aged 6 months until their 5th birthday,
- Pregnant women,
- People 50 years of age and older,
- People of any age with certain chronic medical conditions, and
- People who live in nursing homes and other long term care facilities.
2. People who live with or care for those at high risk for complications from flu, including:
- Household contacts of persons at high risk for complications from the flu (see above)
- Household contacts and out of home caregivers of children less than 6 months of age (these children are too young to be vaccinated)
- Health care workers.
3. Anyone who wants to decrease their risk of influenza.
Who Should Not be Vaccinated?
Some people should not be vaccinated without first consulting a physician. They include:
- People who have a severe allergy to chicken eggs.
- People who have had a severe reaction to an influenza vaccination in the past.
- People who developed Guillain-Barré syndrome (GBS) within 6 weeks of getting an influenza vaccine previously.
- Children less than 6 months of age (influenza vaccine is not approved for use in this age group).
- People who have a moderate or severe illness with a fever should wait to get vaccinated until their symptoms lessen.
