Is it true that the flu shot can give you the flu?

Is it true that the flu shot can give you the flu?

No. No, it can't. No, really – it can't. Honestly, it's impossible to catch the flu from a flu shot!

Every year, rumors like these start flying:

"The flu shot can give you the flu."

"Last year I got a flu shot, and the next day I had the flu."

"My son had a flu shot last year, and he got the flu anyway."

Like many vaccines, the influenza shot contains inactivated viruses. And there's no way to contract even a mild version of a disease from a killed virus. What a flu shot can do is cause minor side effects, including:

  • Soreness, redness, or swelling at the injection site
  • Slight fever
  • Aches

Most people have just a sore arm, if anything. If you do experience side effects, they develop soon after the shot and only last for a day or two. And any side effects from the shot are much milder than flu symptoms.

(Unlike the flu shot, FluMist, the nasal spray flu vaccine, does contain live viruses, but they're weakened and can't survive the warm temperature in your lungs. However, the nasal spray flu vaccine should not be given to pregnant women.)

If you do happen to get the flu within two weeks after getting the shot, don't blame the vaccine: It takes about two weeks for your body to develop the antibodies that will protect you. Until then, you're vulnerable to all flu viruses in your community, even the ones you were just vaccinated against.

Flu vaccines protect best against the three or four influenza viruses that are expected to be most common in a given year. To reduce your risk, get the vaccine as early in the season as possible.

Unfortunately, the flu vaccine doesn't protect against every influenza virus. If you get a bad flu or flu-like illness later in the season, it's probably from a different virus – and there are always plenty of those around. But the flu shot does provide some protection and helps prevent flu-related complications if you're infected by a different, but related, strain of influenza.

A flu shot also can't protect against viruses that aren't in the influenza family. These can cause colds and other respiratory illnesses, which are often hard to distinguish from the flu.

For more information, check the CDC's flu site or call the CDC at (800) 232-4636 (800-CDC-INFO).

Learn more:

Is it safe to get a flu shot during pregnancy?
Get the scoop on flu vaccines for children
How to recognize the signs of flu in children

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