The flu vaccine can cause side effects, but they are generally mild and go away on their own within a few days. Common side effects from the flu shot include:

• Soreness, redness, and/or swelling where the shot was given
• Headache
• Fever
• Nausea
• Muscle aches

In rare cases, the flu shot can cause severe allergic reactions, but these are very rare. Signs of a serious allergic reaction can include breathing problems, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness. If these symptoms occur, it is usually within a few minutes to a few hours after receiving the shot.

If you experience severe or excessive side effects, or if you have any concerns about your reaction to the flu vaccine, you should contact your healthcare provider. You can also report suspected side effects of vaccines and medicines through the Vaccine Adverse Event Reporting System (VAERS) or the Yellow Card Scheme.