Skip to main content

What are the side effects of the flu shot?

Medically reviewed by Drugs.com. Last updated on Aug 28, 2023.

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

Related questions

Read next

COVID-19 vaccines and variants: What you should know

The top 3 SARS-CoV-2 variants in the U.S. in early December 2023 are all of Omicron lineage and include: HV.1 (30%), JN.1 (21%) and EG.5 (9%). Currently the JN.1 variant is increasing, while HV.1 seems to be decreasing. These percentages are based on modeled predictions of variant proportions. Continue reading

Can you overdose on Nyquil?

Yes, you can overdose on Nyquil if you take more than recommended, give a child more than is recommended, or you give Nyquil to a child who is under the age of 6 years. Continue reading

Phenylephrine vs Pseudoephedrine - How do they compare?

The most important difference between phenylephrine (PE) and pseudoephedrine is that phenylephrine is ineffective at relieving nasal congestion, whereas there is some evidence that oral pseudoephedrine is effective. Continue reading

Related medical questions

Related support groups

Medical Disclaimer