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DOI:
https://doi.org/10.57187/4794

Original article

Vol. 156 No. 9 (2026)

Hospitalisations with myocarditis before and during the COVID-19 pandemic – a nationwide cohort study

Cite this as:
Swiss Med Wkly. 2026;156:4794
Published
24.09.2026

Summary

AIMS OF THE STUDY: Over the past decade, there has been a steady increase in myocarditis cases, paralleling the expanded availability and use of cardiac magnetic resonance imaging. Although some have speculated that COVID-19 or its vaccines may be contributing to this increase, recent studies have not provided conclusive proof. Therefore, this study aims to analyse the association between COVID-19 and myocarditis in hospitalised patients.

METHODS: In this nationwide cohort study, the primary outcome was trends in hospitalisations with myocarditis before (years 2012-2019) and during (years 2020-2022) the COVID-19 pandemic. Trends were calculated using linear mixed-effects segmented regression models. Secondary outcomes included in-hospital mortality, intensive care unit admission, length of stay, and 30-day hospital readmission. Results were stratified by sex and age for subgroup analyses.

RESULTS: During the pre-pandemic period, 4,304 hospitalisations with myocarditis were recorded, compared with 2,749 during the pandemic. The incidence rate of myocarditis increased from 26.7 cases per 100,000 hospitalisations in 2012 to 73.8 per 100,000 in 2022 (p for trend <0.001). The quarterly slope of incidence rose significantly during the pandemic (slope, 2.008 [95% CI: 2.006 to 2.011]) compared with that during the pre-pandemic period (slope, 1.141 [95% CI: 1.140 to 1.141]). Subgroup analyses showed the steepest increases in young and middle-aged males. Sensitivity analyses based on the Swiss population confirmed this pattern, with a population-adjusted quarterly increase in myocarditis hospitalisations from 1.0 to 2.6 per 100,000 inhabitants between 2012 and 2022 (p for trend <0.001).

CONCLUSION: This nationwide cohort study found a marked increase in the incidence of hospitalisations with myocarditis during the COVID-19 pandemic, suggesting a causal relationship between COVID-19 infection and/or its vaccination and the increased incidence of myocarditis.

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