Background: Previous literature suggests that both SARS-CoV-2 infection and COVID-19 mRNA vaccine are associated with myocarditis, in which the incidence is higher in the infection group. COVID-19 mRNA vaccine-related myocarditis is noted to have a more benign course. Despite these findings, there is a need for a larger population systematic review that compares the outcomes to pre-pandemic acute myocarditis to better understand the extent of the current post-COVID state.
Methods: We performed a literature search with PubMed and EMBASE and identified studies investigating COVID-19 and its vaccinated population, and the population prior to the pandemic (control group) who had myocarditis. We performed a one-group meta-analysis of the incidence, baseline demographics, and outcomes of myocarditis for each group.
Results: The incidence in the SARS-CoV-2 infection group was 2.76 per thousand (95% CI, 0.85-8.92), 19.7 per million (95% CI, 12.3-31.6) in the vaccine group, and 0.861 per million (95% CI, 0.04-16.7) in the control group. The majority of patients were male, with the highest proportion in the vaccine group. The mean age was the youngest in the vaccine group (24.8, 95% CI, 19.1-30.6). The vaccine group had the lowest mortality (2.0%, 95% CI, 1.3-2.7) followed by the control and the SARS-CoV-2 infection group. The vaccine group had the lowest proportion of immunoglobulin and glucocorticoid use, mechanical circulatory support, and cardiogenic shock.
Conclusion: Our study showed favorable outcomes of myocarditis in patients with COVID-19 mRNA vaccination, despite a higher incidence than pre-COVID controls. Further studies with standardized myocarditis diagnostic criteria assessing long-term outcomes are necessary.
Keywords: COVID-19; Myocarditis; SARS-CoV-2; mRNA vaccine.
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