The best time to get a flu shot is during September or October before the flu season ramps up, ideally before the end of October. This timing balances getting protection before the flu season peaks (usually December through February) and ensuring immunity doesn't decline too much before the season ends. It takes about two weeks after vaccination to build sufficient protection. For some groups, such as pregnant women in their third trimester, children who need two doses, or those with special circumstances, earlier vaccination may be recommended. In summary:
- General recommendation: Get vaccinated in September or October, before the end of October.
- Pregnant women in third trimester: Vaccinate earlier for baby’s protection.
- Children needing two doses: Start early to complete series on time.
- Vaccination later in the season is still better than not at all if missed earlier.
This guidance is based on 2025-2026 flu season recommendations from health experts including the CDC.
