The Moderna vaccine, like all vaccines, may cause side effects in some people. Symptoms are usually mild and resolve after a few days. Some of the symptoms are part of the body’s response to developing immunity to a virus.
The most commonly reported side effects are:
- pain at the injection site
- swelling, and colour changes in the skin (for example, red, purple) at the injection site
- muscle or joint pain
- mild fever
Ongoing studies on the COVID-19 vaccines have found that serious side effects are extremely rare.
Very rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart) following vaccination with COVID-19 mRNA vaccines have been reported. These cases have been reported most frequently in adolescents and younger adults under 30 years of age, more frequently in males compared to females, usually within a week after vaccination, and more frequently after the second dose. These individuals tend to recover quickly.
Individuals should seek medical attention right away if they develop any of the following symptoms after receiving the Moderna vaccine:
- chest pain
- shortness of breath
- feelings of a fast beating, fluttering or pounding heart
The second dose in the mRNA COVID-19 vaccination series should be deferred in individuals who experience myocarditis or pericarditis following the first dose of an mRNA COVID-19 vaccine, until more information is available.
As a precaution, children who experience myocarditis and/or pericarditis after a first dose of the vaccine should wait to get a second dose until more information is available. Children who have a history of myocarditis unrelated to COVID-19 vaccination should consult their clinical care team for individual considerations and recommendations. If they are no longer under active care for myocarditis, they may receive the vaccine. Caregivers should be advised to seek medical attention for children if they develop symptoms including chest pain, shortness of breath, or palpitations following receipt of a COVID-19 vaccine.
Learn more about Myocarditis and Pericarditis (PDF file).
Speak with your health care professional about any serious allergies or health conditions before receiving the Moderna COVID-19 vaccine.
Vaccine side effects will continue to be monitored as people receive the vaccine. If you get a reaction to the vaccine, contact your health care provider who will report the side effect directly to public health. Public health will keep track of the reported side effects to make sure the vaccine continues to be safe.