How Long Does It Take for the Flu Shot to Be Effective?

Here's what a doctor who treats the flu says.

Flu season has arrived—and if you haven't gone for your annual flu shot yet, you've probably at least penciled it into your calendar (hint hint). Seriously, there's no reason not to. The flu vaccine is simple, takes zero time, and is the best way to reduce your odds of spending a week in flu agony.

But there's one thing the flu shot can't do: safeguard you from the flu immediately. In fact, the vaccine needs some time to work its magic.

“It takes about two weeks after getting the vaccine for your body to build up enough antibodies to protect against the flu,” Jean Moorjani, MD, a pediatrician at Orlando Health Arnold Palmer Hospital for Children, tells Health. That means the flu could still creep up on you during that two-week waiting period.

This is why it's important not to see your flu shot as a hall pass and let other flu-preventing precautions fall to the side. You still need to get enough sleep, maintain a healthy diet, and stick to your workout schedule to keep your immune system in fighting shape in case you do encounter the flu virus.

And of course, wash your hands with soap and water (or use hand sanitizer if you can't find a sink) regularly—especially before you eat or touch your eyes, nose, or mouth, all of which are conduits that allow flu viral particles to enter your body and infect you. Even after the two-week wait, never slack on these anti-flu measures.

Also, if you’re wondering if you really need the flu shot, the answer is 100% yes. The Centers for Disease Control (CDC) recommends that just about everyone over the age of six months get vaccinated.

“We always encourage everybody to get vaccinated as soon as possible,” asserts Dr. Moorjani. Since you need to give your body two weeks to build up those flu antibodies, it’s crucial you get your vaccine before the end of October, she says. No one wants to enter the thick of flu season, which ramps up in November and December, without proper protection.

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