(NEXSTAR) – Pharmacies are stocked with a new batch of flu shots, but that doesn’t mean you need to rush out and get one. Health experts, who you’ve often heard urging vaccination as soon as possible, are instead suggesting it may not be the ideal time for most people to get their annual influenza vaccine.

Timing the flu vaccine perfectly is tricky, but you’ll want to get it ahead of peak flu season, the Centers for Disease Control and Prevention advises. Flu activity tends to pick up around October, peak between December and February, and decrease throughout the spring season.

The CDC says most people should try to get the flu vaccine in September or October, but definitely by the end of October.

“You really want to think about getting your appointment or making your plan to get vaccinated sometime around the last half of September through the end of October,” Dr. Judith O’Donnell, chief of infectious diseases at Penn Presbyterian Medical Center, told NBC News.

A recent study of 800,000 pediatrician visits found that children who got vaccinated in October were also least likely to be diagnosed with influenza that season.

Waiting until the latter half of September or October to get the shot can offer you protection for a bit longer, through the end of peak flu season. It takes about two weeks for the vaccine to be fully effective, the CDC says.

The advice to wait a few more weeks applies to most people, but elderly people and those with chronic health conditions should consult their doctor to make the decision that works best for their individual risk level and exposure.

Some children between 6 months and 8 years old should get a vaccine sooner, the CDC advises, because they’ll need two doses. Pregnant people in the third trimester may also want to consider getting vaccinated early.

If you don’t think you’ll be able to get vaccinated in October, it’s better to get one now than not at all. You may want to make things easier for yourself by getting a COVID-19 booster at the same time, which health experts say is safe to do.

“If we could have a crystal ball, then we’d be able to time things just right,” Scott Hensley, a microbiology professor at the University of Pennsylvania, said in an interview with STAT. “There’s risk in waiting, and there’s risk in getting it too soon.”

Even if you miss the ideal window, it’s still beneficial to get vaccinated later in the flu season as long as the influenza virus is still circulating.