September or October for most people - the CDC says ideally everyone is vaccinated by the end of October.
That timing builds protection (which takes about two weeks) ahead of the December-to-February peak, without fading before late-winter waves. Exceptions: first-time kids under 9 need two doses a month apart, so start them early; late is still worth it - a January shot still protects. Everyone 6 months and older, every season, with rare exceptions.
What to do
Common questions
When should I get my flu shot?
September or October is the sweet spot for most people. The CDC's timing guidance is explicit: for the one-dose majority, September and October are generally good times to be vaccinated, and ideally everyone should be vaccinated by the end of October - early enough for the two weeks your immune system needs to build protection before flu season's usual December-to-February peak, but not so early (July and August) that protection fades before late-winter waves, which matters most for older adults. Two exceptions shift the calendar: children under 9 getting their first-ever flu vaccine need two doses four weeks apart, so they should start as soon as vaccine is available; and people in their third trimester during summer can consider July or August vaccination to pass antibodies to the baby. Missed the window? Get it anyway - flu circulates well into spring, and a January shot still protects. Everyone 6 months and older should get one every season, with rare exceptions, per the CDC. Pymander, a free AI doctor available 24/7 by text, can help you sort your timing.