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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 where you got the shot
  • Slight fever
  • Aches

Most people have just a sore arm, if anything. But if you do experience side effects, they crop up 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, the nasal spray flu vaccine does contain live viruses, but you can't catch the flu from the nasal spray either. The virus is weakened and can't survive the warm temperature in your lungs.

Side effects from the nasal spray for adults include runny nose, headache, sore throat, and cough. Children who receive the spray may develop a runny nose, headache, wheezing, vomiting, muscle aches, and fever.

(Both the flu shot and nasal spray have specific age guidelines, and some people with certain conditions should not receive the flu vaccine. Ask your child's doctor for advice.)

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. (The nasal spray protects against four, and the shot covers three or four depending on the type you receive.) 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 likely from a different virus – and there are always plenty of those around. But it 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.

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