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What are the side effects of the flu shot?

Medically reviewed by Drugs.com Last updated on Sep 17, 2018.

Official Answer

by Drugs.com

The most common side effects of the influenza (flu) vaccine include soreness, redness, and a slight swelling around the injection site AND mild flu-like symptoms such as a headache, a slight fever, muscle aches, and nausea. Most people experience few, if any, side effects.

Injection site reactions:

Because most flu vaccines are given as an injection into a muscle, the most commonly reported side effects involve those associated with a needle piercing the skin, such as soreness, redness, and a slight swelling around the injection site. A slight, sharp pain may be experienced as the shot is delivered; however, this is usually short lasting. FluMist is a flu vaccine that is given as a nasal spray, but it isn’t for everybody. Side effects associated with FluMist include a runny nose, headache, sore throat, and cough.

Other common side effects:

The influenza vaccine contains proteins that stimulate your immune system to make antibodies against the influenza virus. The flu vaccine will not give you the flu but may cause mild flu-like symptoms, such as a headache, a slight fever, muscle aches, and nausea. These usually go away within a few days. People who are prone to fainting may faint when they are administered the flu shot, just like they would with any other vaccine.

Allergic reactions:

Very severe or life-threatening allergic reactions to the flu vaccine are rare. Symptoms usually come on within a few minutes of having the vaccine and include difficulty breathing or wheezing, dizziness, facial or throat swelling, hives or an extensive rash, a fast heartbeat or chest pain, and sometimes collapse. If you or someone you know is having a severe allergic reaction to the flu vaccine call 911.

The best way to reduce your chances of catching the flu every year is to get a flu shot. In fact, the CDC (Centers for Disease Control and Prevention) recommends everybody over the age of six months receive the flu vaccine every year, with a few exceptions.

For more information see Influenza Vaccine

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