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. 2023 Feb 8;76(3):e544-e552.
doi: 10.1093/cid/ciac446.

Analysis of Myocarditis Among 252 Million mRNA-1273 Recipients Worldwide

Affiliations
Free PMC article

Analysis of Myocarditis Among 252 Million mRNA-1273 Recipients Worldwide

Walter Straus et al. Clin Infect Dis. .
Free PMC article

Abstract

Background: Growing evidence indicates a causal relationship between SARS-CoV-2 infection and myocarditis. Post-authorization safety data have also identified myocarditis as a rare safety event following mRNA COVID-19 vaccination, particularly among adolescent and young-adult males after dose 2. We further evaluated the potential risk by querying the Moderna global safety database for myocarditis/myopericarditis reports among mRNA-1273 recipients worldwide.

Methods: Myocarditis/myopericarditis reports from 18 December 2020 to 15 February 2022 were reviewed and classified. The reported rate after any known mRNA-1273 dose was calculated according to age and sex, then compared with a population-based incidence rate to calculate observed-to-expected rate ratios (RRs).

Results: During the study period, 3017 myocarditis/myopericarditis cases among 252 million mRNA-1273 recipients who received at least 1 dose were reported to the Moderna global safety database. The overall reporting rate was 9.23 per 100 000 person-years, which was similar to the expected reference rate (9.0 cases per 100 000 person-years; RR [95% confidence interval (CI)], 1.03 [.97-1.08]). When stratified by sex and age, observed rates were highest for males aged <40 years, particularly those 18-24 years (53.76 per 100 000 person-years), which was higher than expected (RR [95% CI], 3.10 [2.68-3.58]). When considering only cases occurring within 7 days of a known dose, the observed rate was highest for males aged 18-24 years after dose 2 (4.23 per 100 000 doses administered).

Conclusions: Myocarditis/myopericarditis rates were not higher than expected for the overall population of mRNA-1273 recipients but were higher than expected in males aged 18-24 years, with most cases occurring 7 days after dose 2.

Keywords: COVID-19; SARS-CoV-2; myocarditis; pharmacovigilance; vaccination.

Conflict of interest statement

Potential conflicts of interest. All authors are employees of and shareholders in Moderna, Inc. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

None
Graphical summary describing the main outcomes of a surveillance study assessing the rates of myocarditis among 252 million mRNA-1273 recipients worldwide. Reports of myocarditis were obtained from the Moderna global safety database between December 18, 2020 and February 15, 2022. Abbreviations: COVID-19, coronavirus disease 2019; mRNA, messenger RNA; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
Figure 1.
Figure 1.
Distribution and time to onset of myocarditis and myopericarditis cases after mRNA-1273. (A) Distribution of the 3017 reported myocarditis and myopericarditis cases among mRNA-1273 recipients according to age and sex. A total of 317 cases were missing age and/or sex information. (B) Timing of the 518 reported cases of myocarditis and myopericarditis after dose 1, 1201 reported cases of myocarditis and myopericarditis after dose 2, and 175 reported cases of myocarditis and myopericarditis after dose 3. A total of 1123 cases were missing dose number information.

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