Can mRNA vaccines cause myocarditis and pericarditis?

Question: 

Can mRNA vaccines cause myocarditis and pericarditis?

Answer: 
In rare cases, people have experienced myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart) following vaccination with COVID-19 mRNA vaccines. 
 
  • In Canada, this has occurred at a rate of about 1.7 cases per 100,000 doses of Moderna vaccine and 1.1 cases per 100,000 doses of Pfizer-BioNTech vaccine for older children and adults.
  • The risk of myocarditis is much greater following COVID-19 infection than following vaccination.
  • The majority of affected people, even if hospitalized, have experienced relatively mild illness, responded well to conservative treatment, and recovered quickly.
Cases of myocarditis and pericarditis following COVID-19 mRNA vaccination occur:
 
  • Most commonly in males 18-29 years of age.
  • Most often after the second dose. 
  • More often in males than females. 
  • More often after the Moderna vaccine than the Pfizer-BioNTech vaccine. (5 times higher with the Moderna vaccine compared to the Pfizer-BioNTech vaccine)
Myocarditis and pericarditis following vaccination in children 5 to 11 years of age:
 
The rate of cases in younger children is much lower. In the US, this occurred at a rate of about 2.7 cases per 1,000,000 doses of Pfizer vaccine in males 5-11 years of age. Rates for children 6 months to less than 5 years of age are unknown at this time. It is expected that cases will be very rare and rates will be lower than the rates for those older than 5 years of age.
 
Symptoms of myocarditis and pericarditis to look out for:
 
  • Chest pain.
  • Shortness of breath.
  • Feeling of a rapid or abnormal heart rhythm.
If your child experiences these symptoms, seek medical attention right away. Inform the health care provider that your child received a COVID-19 vaccine recently.
Date last reviewed: 
Monday, Aug 08, 2022