COVID 19: Risk of Myocarditis Highest Following Second Vaccine Dose Among Adolescent and Young Adult Males Interview with:

Dr. Oster

Matthew Oster, MD, MPH
CDC COVID-19 Response
CDC Center on Birth Defects and Developmental Disabilities
Pediatric Cardiologist, Sibley Heart Center, Children’s Healthcare of Atlanta
Emory University School of Medicine
Emory University Rollins School of Public Health  What is the background for this study?  What are the main findings?

Response: More than 192 million people ages 12 years and older in the U.S. received at least one dose of mRNA COVID-19 vaccines from December 2020 through August 2021. From this population, VAERS (the Vaccine Adverse Event Reporting System) received 1,991 reports of myocarditis,  1,626 of which met the case definition of myocarditis. Rates of myocarditis were highest following the second dose of an mRNA vaccine among males aged 12–15 years (70.7 per million doses of Pfizer), 16-17 years (105.9 per million doses of Pfizer), and 18–47 years (52.4 and 56.3 per million doses of Pfizer and Moderna, respectively).

Of those with myocarditis, the median age was 21 years and the median time from vaccination to symptom onset was two days. Males accounted for 82% of patients for whom sex was known. Approximately 96% were hospitalized, 87% of whose symptoms had gone away by the time they were discharged from the hospital. Non-steroidal anti-inflammatory drugs (589/676, 87%) were the most common treatment. What should readers take away from your report?

Response: The risk of myocarditis was highest following the second vaccine dose among adolescent and young adult males. This risk should be considered within the context of the significant benefits of COVID-19 vaccination in preventing COVID-19 infection and potential serious complications from COVID-19. The benefits of COVID-19 vaccination continue to outweigh any potential risks, including myocarditis. CDC recommends that everyone ages 5 years and older get vaccinated as soon as possible which includes receiving a booster dose when eligible. What recommendations do you have for future research as a result of this work?

Response: Long-term outcome data are not yet available for COVID-19 vaccine-associated myocarditis patients. CDC is currently following patients reported to VAERS with confirmed myocarditis after receiving an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna). By conducting follow-up surveys with both patients and healthcare providers 3-6 months after the myocarditis episode CDC can assess long-term health outcomes, collect important data, and continue to ensure the safety of COVID-19 vaccines. For more on these follow-up efforts, visit: Investigating Long-Term Effects of Myocarditis | CDC

Initial results of these follow-up investigation efforts presented in November to the Advisory Committee on Immunization Practices (ACIP) included the finding that 91% of cardiologists or healthcare providers surveyed about their patients’ status said that their patients were fully or probably recovered. Most (83%) patients who received an electrocardiogram three months after their myocarditis diagnosis had a normal result.

Is there anything else you would like to add? Any disclosures?

No disclosures.

  • While the most commonly reported heart problem following COVID-19 vaccination has been myocarditis, this has been rare. Heart problems that have more commonly occurred after infection with COVID-19, including:
  • Myocarditis from active COVID-19 infection
  • Heart conditions associated with Multi Inflammatory Syndrome in Adults and Children (MIS-C and MIS-A), a condition where different parts of the body become inflamed

An MMWR published in September 2021 looked at the relationship between COVID-19 infection and myocarditis and found that patients with COVID-19 had 16 times the risk of myocarditis as patients who did not have COVID-19, with level of risk varying by sex and age.

  1. This study focused on those ages 12 and over. A recent MMWR published on Dec. 30, 2021, looked at preliminary vaccine safety data in children ages 5-11 years and found that myocarditis among children in this age group appears to be even more rare. As detailed in the report, from November 3–December 19, 2021, CDC reviewed reports to VAERS as well as to v-safe, a voluntary smartphone-based COVID-19 vaccine safety surveillance system. Of those reports, there were 11 verified cases of myocarditis among children 5-11 years old that occurred after administration of 8.7 million vaccine doses. COVID-19 vaccines are safe and effective for children, including young children. 


Oster ME, Shay DK, Su JR, et al. Myocarditis Cases Reported After mRNA-Based COVID-19 Vaccination in the US From December 2020 to August 2021. JAMA. 2022;327(4):331–340. doi:10.1001/jama.2021.24110

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Last Updated on January 25, 2022 by Marie Benz MD FAAD