Is There a Causal Link Between Acute Myocarditis and COVID-19 Vaccination: An Umbrella Review of Published Systematic Reviews and Meta-Analyses.

Introduction: A few months after the beginning of the coronavirus disease of 2019 (COVID-19) vaccination, several reports of myocarditis secondary to the vaccines were published, sometimes with fulminant cases, but until today there is no proven causal link between these 2 events, but with many hypotheses proposed.

Methods: A systematic review of current evidence regarding myocarditis after COVID-19 vaccination was performed by searching several databases including PubMed/Medline and Web of Science. The quality of Meta-analysis was assessed using the AMSTAR-2 tool as well as other qualitative criteria.

Results: Our umbrella review appraised 4 Meta-analysis of retrospective studies (range: 5-12), The number of vaccine doses included ranged from 12 to 179 million, with the number of myocarditis cases observed ranging from 343 to 1489. All types of vaccines were evaluated, with no exclusions. The overall incidence ranged from 0.89 to 2.36 cases of myocarditis per 100 000 doses of vaccine received. Heterogeny was assessed in 3 of the Meta-analysis, and was highly significant (>75%) in all included studies, and with a significant P-value (P < .05). Regarding publication bias, 3 of the Meta-analysis conducted the egger and begg regression, with a significant result in only 1. Regarding the assessment of the methodology by the AMSTAR-2 scale indicating that the quality was very critical in 1, low in 2, and moderate in 1 Meta-analysis.

Conclusion: The quality of current non-randomized evidence on real causality and incidence of myocarditis after COVID-19 vaccine is still low.