The best time to get a flu shot is generally in September or October. This timing helps ensure protection before flu season begins, which typically starts in October and peaks between December and February. Your body takes about two weeks after vaccination to build enough immunity, so getting vaccinated by the end of October offers optimal protection. For certain groups, such as pregnant women in their third trimester, vaccination can be encouraged earlier, starting in July or August, to protect newborns. Older adults (65+) are advised to wait until September or later for their shot to avoid waning protection too early. If missed, getting vaccinated later in the season, even after December or into January, can still provide meaningful protection since flu activity can continue through May. In summary:
- Most people: September to October
- Pregnant women (third trimester): July or August
- Older adults (65+): September or later
- Late vaccination still better than none
This timing balances early protection with the longevity of vaccine effectiveness throughout the flu season.
