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VERIFY: Flu Shot Can’t Cause The Flu, But It Can Make You Feel Sick

You ask; we VERIFY. The flu shot can’t give a person the flu, but it can make him or her feel sick for a number of reasons.

GREENSBORO, N.C. — It's time to stick a needle in social media misinformation -- and the dangerous claims preventing people from getting vaccinated for the flu.


Perhaps the biggest false statement about the flu vaccine is that it can cause the flu. All three of the sources below confirm the flu vaccines contain either a dead flu virus or a single-gene virus, which can cause an immune response without an infection. 

So, if the flu shot cannot cause the flu, why do some people swear the flu shot makes them sick?



Mayo clinic explains a number of reasons why a flu vaccine could cause someone to feel sick.

1) Reaction to vaccine -- if someone has a fever and aches for a day or two after the vaccine, the body is likely building up protective antibodies. Those symptoms are signs the vaccine is doing what it is supposed to be doing.

2) Two-week effectiveness -- it takes two weeks for the flu vaccine to take full effect. If you are exposed to the flu virus shortly before or during that time, you can catch the flu.

3) Vaccine mismatch -- the vaccine does not match the virus that is circulating. Keep in mind, researchers develop the vaccine well ahead of flu season, so they essentially have to guess which strain will be the most common. If a mismatch happens, the vaccine will not be as effective but still can give some protection.

4) Other illness -- perhaps you are coming down with a cold or respiratory illness with flu-like symptoms. You're sick, but it is not from the flu, and the vaccine did not cause you to feel that way.

5) Severe allergy -- some people might have severe allergic reactions to ingredients in the vaccine, like eggs, for example. In these cases, a doctor might recommend a vaccine option without egg proteins.

Note the nasal spray version of the vaccine does include a live flu virus, but it is too weak to cause the flu. Side effects of the nasal spray can include a runny nose, wheezing, headache, vomiting and muscle aches. These are usually short-lived side effects and much less severe than symptoms caused by the flu illness.


Yes, the flu shot can make you feel sick...briefly. But, it's likely because your body is responding appropriately and building antibodies. Just know the flu vaccine did not give you the flu.

Do you have a VERIFY inquiry? Submit a post or selfie video to Meghann Mollerus via:

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