Like any vaccine, COVID-19 vaccines can cause mild side effects, such as a low-grade fever or pain or redness at the injection site. Most reactions to vaccines are mild and go away within a few days on their own. More serious or long-lasting side effects to vaccines are possible but extremely rare. Vaccines are continually monitored to detect rare adverse events.

Reported side effects to COVID-19 vaccines have mostly been mild to moderate and short-lasting. They include: fever, fatigue, headache, muscle pain, chills, diarrhoea, and pain at the injection site.