Medical Technology

COVID mRNA Vaccine Cardiac Effects Rare in Kids, Adolescents

This is a summary of a preprint research study written by authors from London on MedRxiv, provided to you by Medscape.

This study has not yet been peer-reviewed. The full text of the study can be found on

Key Takeaways

  • Cardiac adverse effects — myocarditis, pericarditis, and/or myopericarditis — are very rare after mRNA vaccination for COVID-19 in 12- to 17-year-olds, suggests a systematic review of 21 peer-reviewed reports.

  • Most patients presented with chest pain about 2 days after vaccination, and usually after the second dose.

  • Of the 85% of patients who were hospitalized, most were discharged in 2 to 7 days without treatment other than nonsteroidal anti-inflammatory drugs (NSAIDs). Corticosteroids were used in about 15%.

  • The clinical picture of myocarditis was broadly similar to what has been previously reported across all ages. Most cases were mild and self-limited without significant treatment.

Why This Matters

  • Case reports of myocarditis, mostly in boys, were published soon after 12- to 17-year-olds in several countries began vaccinations against COVID-19 in May. By October, there were several reports citing widely different rates.

  • This review synthesizes the latest data on adverse cardiac effects in 12- to 17-year-olds after they were immunized against COVID-19.

  • The findings can help inform national vaccination strategies and clinical decision-making, as countries expand adolescent vaccination and consider extending vaccination to younger children.

Study Design

  • The researchers identified 21 articles — 17 of which were case reports or series and four of which were pharmacovigilance studies — on myocarditis, pericarditis, and/or myopericarditis in 12- to 17-year-olds related to vaccination against SARS-CoV-2.

  • They were published from December 1, 2019 to September 14, 2021 and supplemented with data from passive-surveillance registries through November 13, 2021.

  • Three studies used data from three passive surveillance databases:

    • the European Medicines Agency’s European database of suspected adverse drug reaction reports (EudraVigilance).

    • the United States Centers for Disease Control (CDC) Vaccine Adverse Event Reporting System (VAERS).

    • the World Health Organization’s global Individual Case Safety Report Database (VigiBase).

  • One study describing 22 cases used data from the CDC’s active surveillance Vaccine Safety Datalink (VSD).

Key Results

  • The case reports and case series articles provided detailed adverse cardiac effects in 127 people, 117 in the United States, nine in Israel, and one in Germany.

    • 64 patients had myocarditis and 56 patients had myopericarditis.

    • 126 patients (99%) presented with chest pain. All 127 showed elevated troponin, and 93 patients (74%) had an abnormal ECG. Cardiovascular MRI in 91 patients identified myocardial injury in 56 (62%).

    • 92 of 121 patients were treated with NSAIDs.

  • The adverse cardiac event rate in 12- to 17-year-olds, based on VSD data, was estimated at 29.6 per million vaccinated.

  • The American and European passive surveillance registries contained 1129 reports of myocarditis and 358 reports of pericarditis in the age group, which likely included some or all of the published and active-surveillance cases.

  • In the VAERS database, the rate of myocarditis per million 12- to 17-year-olds vaccinated was 12.4 for boys and 1.4 for girls after the first dose, and 49.6 for boys and 6.1 for girls after the second dose. Reported levels were highest soon after the initiation of vaccines in this age group, suggesting possible reporting bias.


  • Less-severe cases may not have been reported.

  • Estimates from passive vaccine surveillance systems lack comparison groups, and have been based on under-reporting.

  • Cardiac effects may differ in children younger than 12 years.

  • Data were insufficient to compare the risk for cardiac events with the Pfizer-BioNTech and Moderna vaccines in this age group.

  • Larger and more detailed longitudinal studies based on active-surveillance sources are needed.


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