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Rare Myocarditis Risk following COVID-19 Vaccine

  • CDC/MMWR
Jul 12, 2021 2:19 pm

MMWR review of the risk of myocarditis and pericarditis reports a June 23, 2021 recommendation by the Advisory Committee on Immunization Practices that the benefits of COVID-19 vaccination clearly outweighed the risks of myocarditis after vaccination. 

The COVID-19 vaccines from Pfizer-BioNTech and Moderna were issued Emergency Use Authorizations (EUAs) for the prevention of COVID-19 in December 2020 In December 2020. While initially approved for use in persons aged ≥16 years and ≥18 years, respectively, this was expanded to adolescents aged 12–15 years in May 2021. 

The ACIP recommends that all persons aged ≥12 years receive a COVID-19 vaccine.

Recently there have been reports of myocarditis and pericarditis in mRNA vaccine recipients, predominantly in young males and mostly after the second dose.  Hence, most cases were largely reported in children, adolescents and young males.  Myocarditis cases per million (following the 2nd mRNA vaccine dose) dropped by age group from 56–69 (12-17 yrs old), to 45–56 (18-24 yrs), to 15–18 (25-29 yrs), to 3–4 cases per million (≥ 30 yrs).

A new ACIP meeting was convened on June 23, 2021 to review these reports of myocarditis and pericarditis and discuss the overall benefits and risks of mRNA COVID-19 vaccination in the United States.

As of June 11, 2021, approximately 296 million doses of mRNA COVID-19 vaccines had been administered in the United States, with 52 million administered to persons aged 12–29 years.

There were 1,226 reports of myocarditis following mRNA vaccination (within 7 days) between December 29, 2020–June 11, 2021.  The median age of these cases was 26 years, with median symptom onset of 3 days after vaccination.  Over 76% noted the onset following the second dose of mRNA vaccine (with both Pfizer-BioNTech and Moderna vaccines).

The validity of the diagnosis was confirmed in 323 of these 484 cases by CDC investigators. The median age of this cohort was 19 years (90% male), with a median symptom onset of 2 days and 92% experiencing symptoms within 7 days of vaccination.  Most (96%) were hospitalized, but mild with 95% havingbeen discharged at time of review. there were no deaths.

The ACIP reviewed the potential benefits of vaccination (prevention of COVID-19 disease and associated hospitalizations, ICU admissions, and deaths) numerically demonstrating the prevention numbers outweighed the risks (expected myocarditis cases after vaccination) in all populations recommended for vaccination.  Even for the older less affected group (males >30 yrs), COVID-19 vaccination would prevent 15,300 COVID-19 cases, 4,598 hospitalizations, 1,242 ICU admissions, and 700 deaths; compared with three to four expected myocarditis cases after COVID-19 vaccination.

ACIP concluded:

  1. The benefits of vaccinating all recommended age groups with mRNA COVID-19 vaccine clearly outweigh the risks of vaccination, including the risk of myocarditis after vaccination;
  2. Continuing to monitor outcomes of myocarditis cases after COVID-19 vaccination is important;
  3. Providers and the public should be informed about these myocarditis cases and the use of COVID-19 vaccines. 
Disclosures
The author has no conflicts of interest to disclose related to this subject

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