The seasonal flu shot is a yearly vaccine administered to protect against the flu, or influenza.
In the United States, flu shots are recommended for everyone ages 6 months and older, according to the Centers for Disease Control and Prevention.
The composition of the 2019-2020 flu shot will be slightly different from last season's flu shot. Specifically, there will be a different strain of the H1N1 virus and a different strain of the H2N3 virus in this season's flu shot, compared with last season's shot.
The CDC is once again recommending the spray during the 2019-2020 flu season, after not recommending the nasal spray in some previous seasons.
Exactly when the flu season starts and ends is unpredictable, so health officials recommend that people get their flu shot in early fall, preferably by the end of October, the CDC says. Flu activity typically peaks in January or February.