Influenza (flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is to get a flu vaccine each fall. Children 6 to 23 months of age are considered at high-risk for flu complications and should be immunized. Consult your health care provider for more information regarding childhood flu immunization recommendations

There are two types of vaccines:

The "flu shot" -- an inactivated vaccine containing a killed virus (sometimes called TIV for “Trivalent Inactivated Influenza Vaccine”) that is given with as an injection. The flu shot is approved for people older than 6 months, including healthy people and people with chronic medical conditions.

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 healthy people 5 years to 49 years of age who are not pregnant.
About two weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body. Flu vaccine is the best way to prevent infection, but everyone must be re-vaccinated each year because the flu viruses change each year.