The best time to get a flu shot is generally in September or October. This timing provides a good balance between getting protection before the flu season starts (which typically begins in October and peaks between December and February) and ensuring immunity lasts through the flu season. It takes about two weeks after vaccination for the body to build up protection, so getting the shot by the end of October is ideal for most people. There are exceptions depending on individual circumstances:
- Children who need two doses should start their vaccinations as soon as the vaccine becomes available.
- Pregnant women in their third trimester may get vaccinated earlier (July or August) to protect their infants after birth.
- Older adults (65 and older) and pregnant women in early pregnancy usually should wait until September or later to avoid waning immunity too early.
- If missed earlier, getting vaccinated later in the season—even as late as January or February—is still better than not getting the vaccine at all, since flu can circulate as late as May.
Overall, the CDC and health authorities recommend getting vaccinated each year by the end of October, but vaccination anytime during the flu season is beneficial for protection.
