Flu vaccines have been in the news a lot lately. But there are actually two different types of vaccines to protect against the seasonal flu (not the 2009 H1N1 flu):
The "Flu Shot"
This is 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.
The Nasal-Spray Flu Vaccine
This is a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "live attenuated influenza vaccine" or FluMist®). LAIV (FluMist) is approved
for use in healthy people 2 to 49 years of age who are not pregnant.
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' estimations about which types and strains of viruses will circulate in a given year.
About two weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body.1
