When is the best time to get a flu shot?

September and October, with the end of October as the target. The CDC says that for most people who need one dose of flu vaccine for the season, September and October are generally good times to be vaccinated, and ideally everyone should be vaccinated by the end of October. The logic: flu usually peaks between December and February, and vaccine protection is strongest in the first months after the shot, so an October shot puts your peak immunity right over the peak season. Getting it in July or August can mean fading protection by the February tail. Getting it in December is still worth it: flu circulates for months, and late vaccination still beats none, which is why the answer to the too-late question is almost always no, as long as flu is spreading. Everyone 6 months and older needs a flu vaccine every year, per the CDC, because the strains change and immunity wanes. If you are 65 or older, pregnant, or have a chronic condition, the timing matters more, not less, because these groups carry the highest risk of complications, so book early in the window rather than hoping to squeeze it in later.