Myocarditis and pericarditis associated with SARS-CoV-2 vaccines: A population-based descriptive cohort and a nested self-controlled risk interval study using electronic health care data from four European countries

Background: Estimates of the association between COVID-19 vaccines and myo-/pericarditis risk vary widely across studies due to scarcity of events, especially in age- and sex-stratified analyses.Methods: Population-based cohort study with nested self-controlled risk interval (SCRI) using healthcare data from five European databases. Individuals were followed from 01/01/2020 until end of data availability (31/12/2021 latest). Outcome was first myo-/pericarditis diagnosis. Exposures were first and second dose of Pfizer, AstraZeneca, Moderna, and Janssen COVID-19 vaccines. Baseline incidence rates (IRs), and vaccine- and dose-specific IRs and rate differences were calculated from the cohort The SCRI calculated calendar time-adjusted IR ratios (IRR), using a 60-day pre-vaccination control period and dose-specific 28-day risk windows. IRRs were pooled using random effects meta-analysis. Findings: Over 35 million individuals (49 & BULL;2% women, median age 39-49 years) were included, of which 57 & BULL;4% received at least one COVID-19 vaccine dose. Baseline incidence of myocarditis was low. Myocarditis IRRs were elevated after vaccination in those aged < 30 years, after both Pfizer vaccine doses (IRR = 3 & BULL;3, 95%CI 1 & BULL;2-9.4; 7 & BULL;8, 95%CI 2 & BULL;6-23 & BULL;5, respectively) and Moderna vaccine dose 2 (IRR = 6 & BULL;1, 95%CI 1 & BULL;1-33 & BULL;5). An effect of AstraZeneca vaccine dose 2 could not be excluded (IRR = 2 & BULL;42, 95%CI 0 & BULL;96-6 & BULL;07). Pericarditis was not associated with vaccination.Interpretation: mRNA-based COVID-19 vaccines and potentially AstraZeneca are associated with increased myocarditis risk in younger individuals, although absolute incidence remains low. More data on children (& LE; 11 years) are needed.

Automated summary

This study found that mRNA-based COVID-19 vaccines and potentially AstraZeneca are associated with increased myocarditis risk in younger individuals, although the absolute incidence remains low. More data on children (≤11 years) are needed.