Planning to get a flu shot this fall? All you need to know about it and why Americans should wait until October

As summer ends and rolls into autumn, the fall season officially begins in the United States of America, and along with that comes the flu season. As fall has kicked in already, many Americans begin seeing flyers and hearing ads for flu shots.However, health experts are advising most people to wait until September or October before getting vaccinated. Why? Timing matters a great deal. Getting a flu vaccine too early can mean your protection weakens before flu activity peaks in winter; too late, and you might get sick before your immune system fully responds.With flu season in the US typically running from October through May, careful planning helps ensure the vaccine works when you need it most.

Fall season and flu shots

Every year, the US Centers for Disease Control and Prevention (CDC) and its Advisory Committee on Immunization Practices (ACIP) release updated guidance for flu vaccination. For the 2025-2026 flu season, they recommend that everyone aged 6 months and older should get an annual flu vaccine, with rare exceptions. But when to get it is just as important as whether you get it.

Why September-October is the sweet spot

One hardly advises delaying a seasonal shot, unless the season stretches on.

Flu season is no different in the US. The following are the key reasons why you should wait till October.Immune protection takes time: After you get a flu shot, your body usually needs about two weeks to build up antibodies strong enough to protect you. If you get vaccinated too early (e.g., in July or early August), that protection may begin to drop off before flu season peaks.Waning immunity: Studies show that vaccine effectiveness declines over time.

The further removed vaccination is from peak flu activity, the more the chance that immunity will have waned. This effect is especially important for older adults.Peak flu season timing: Flu season in the US most often begins in October, with case numbers rising through winter and often peaking between December and February. Vaccinating in September or early October gives people a window of protection before the flu spreads widely.

Who might want or need to get vaccinated earlier

Of course, there are exceptions to the general rule. In fact, some people should consider earlier vaccination:Children aged 6 months through 8 years who need two doses of flu vaccine (if they’ve never had it or didn’t complete the schedule) should get the first dose as soon as the vaccine is available so the second dose is given at least 4 weeks later.Pregnant individuals in their third trimester may get vaccinated earlier (July or August) to ensure that antibodies pass to the baby, protecting the newborn during early life when the infant is too young to get vaccinated themselves.People who may have trouble accessing vaccination later (due to travel, work, or healthcare constraints) may also consider earlier vaccination.

What the CDC is recommending for 2025-2026

For most people, September or October is the ideal time to get vaccinated. The CDC advises that by the end of October, everyone should have had their flu vaccine, if possible.Most adults should avoid getting vaccinated before that (especially those 65+, pregnant in early trimesters) unless there’s a good reason.

This season, all flu vaccines are expected to be trivalent (covering three virus strains), and many single-dose vaccines will be free of thimerosal for children, pregnant women, and adults.However, don’t panic if October passes and you haven’t gotten your flu shot yet. It’s still beneficial to get vaccinated as long as flu viruses are circulating. Even shots given later in the season help reduce the severity of illness, hospitalizations, and deaths.

Safety, efficacy, and practical tips

The flu vaccine is safe for almost everyone 6 months and older. Some vaccine types (shots or nasal spray) depend on age, health status, and vaccine availability. Common side effects, like soreness at the injection site, mild fever, and fatigue, are usually mild. However, watch out for serious side effects, which are quite rare.You can get your flu vaccine at many places: doctors’ offices, pharmacies, clinics, and workplaces. Check your health insurance; many plans cover it fully.