Myocarditis following mRNA Covid-19 vaccination: A pooled analysis

BACKGROUND: Post-marketing surveillance studies have raised concerns of increased myocarditis rates following coronavirus disease-19 (Covid-19) mRNA vaccines. The present study aims to accumulate the published mRNA Covid-19 vaccine-associated myocarditis cases, describe their clinical characteristics and determine the factors predisposing to critical illness. METHODS: Medline, Scopus, Web of Science, CENTRAL and Google Scholar were systematically searched from inception. Studies reporting adult myocarditis cases following BNT162b2 or mRNA-1273 vaccination were included. Individual participant data coming from case reports/series were pooled. Proportional random-effects meta-analysis was conducted by combining the pooled cohort and observational studies with aggregated data. RESULTS: Overall, 39 studies were included with a total of 129 patients. Most cases occurred in young males after the second vaccine dose. Myocarditis after the first dose was significantly associated with prior Covid-19 (p-value: 0.025). The most common electrocardiographic finding was ST-segment elevation, while late gadolinium enhancement was invariably observed in cardiac magnetic reasoning. Logistic regression analysis demonstrated that signs of heart failure were predictive of subsequent critical illness (Odds ratio: 19.22, 95% confidence intervals-CI: 5.57–275.84). Proportion meta-analysis indicated that complete resolution of symptoms is achieved in 80.5% of patients (95% CI: 59.3–92.1), while the proportion of participants necessitating intensive care unit admission is 7.0% (95% CI: 3.8–12.9). CONCLUSIONS: Myocarditis following mRNA Covid-19 vaccination is typically mild, following an uncomplicated clinical course with rapid improvement of symptoms. Future research is needed to define its exact incidence, clarify its pathophysiology and determine the optimal management plan depending on its severity. Protocol registration: dx.https://doi.org/10.17504/protocols.io.bxwtppen.