Myocarditis and Pericarditis After the COVID-19 mRNA Vaccination

Quick Takes

  • The occurrence of myocarditis or pericarditis, or both, after COVID-19 mRNA vaccination was higher compared with pre–COVID-19 background rates but rare.
  • Of note, the risk was highest in men aged 18–25 years, 1–7 days after receipt of the second dose.
  • There were no significant differences in the risk of myocarditis or pericarditis between mRNA-1273 and BNT162b2 COVID vaccine.

Study Questions:

What is the association between myocarditis, pericarditis, or both in people vaccinated with BNT162b2 (Pfizer–BioNTech) or mRNA-1273 (Moderna) COVID-19 vaccine?

Methods:

The investigators conducted a retrospective cohort study, examining the primary outcome of myocarditis, pericarditis, or both, identified using the International Classification of Diseases diagnosis codes, occurring 1–7 days post-vaccination, evaluated in COVID-19 mRNA vaccinees aged 18–64 years using health plan claims databases in the United States. Observed (O) incidence rates were compared with expected (E) incidence rates estimated from historical cohorts by each database. The authors used multivariate Poisson regression to estimate the adjusted incidence rates, specific to each brand of vaccine, and incidence rate ratios (IRRs) comparing mRNA-1273 and BNT162b2. They further used meta-analyses to pool the adjusted incidence rates and IRRs across databases.

Results:

A total of 411 myocarditis, pericarditis, or both, events were observed among 15,148,369 people aged 18–64 years who received 16,912,716 doses of BNT162b2 and 10,631,554 doses of mRNA-1273. Among men aged 18–25 years, the pooled incidence rate was highest after the second dose, at 1.71 (95% confidence interval [CI], 1.31-2.23) per 100,000 person-days for BNT162b2 and 2.17 (95% CI, 1.55-3.04) per 100,000 person-days for mRNA-1273. The pooled IRR in the head-to-head comparison of the two mRNA vaccines was 1.43 (95% CI, 0.88-2.34), with an excess risk of 27.80 per million doses (–21.88 to 77.48) in mRNA-1273 recipients compared with BNT162b2.

Conclusions:

The authors reported that an increased risk of myocarditis or pericarditis was observed after COVID-19 mRNA vaccination and was highest in men aged 18–25 years after a second dose of the vaccine.

Perspective:

This large cohort study reported that the occurrence of myocarditis, pericarditis, or both, after COVID-19 mRNA vaccination was higher compared with pre–COVID-19 background rates but rare (with only 411 events occurring in 15 million recipients of 16,912,716 doses of BNT162b2 and 10,631,554 doses of mRNA-1273). Of note, the risk was highest in men aged 18–25 years, 1–7 days after receipt of the second dose. Furthermore, there were no significant differences in the risk of myocarditis or pericarditis between mRNA-1273 and BNT162b2 vaccines. Given the uncertainty in the risk estimates because of the low number of events, additional studies and data are needed to verify these findings.

Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Heart Failure and Cardiomyopathies, Pericardial Disease, Prevention, CHD and Pediatrics and Arrhythmias, CHD and Pediatrics and Prevention, Acute Heart Failure

Keywords: COVID-19, COVID-19 Vaccines, Heart Failure, Myocarditis, Pericarditis, Primary Prevention, RNA, Messenger, Vaccination, Young Adult


< Back to Listings