Myocarditis after COVID‐19 mRNA vaccination: A systematic review of case reports and case series

BACKGROUND: The coronavirus disease of 2019 (COVID‐19) is a global pandemic with over 266 million cases and 5 million deaths worldwide. Anti‐COVID‐19 vaccinations have had exceptional success in subduing the incidence, prevalence, and disease severity of COVID‐19, but rare cases of myocarditis have been reported after COVID‐19 vaccinations. HYPOTHESIS: Myocarditis occurring after COVID‐19 mRNA vaccinations have distinguishable clinical characteristics. They usually have a favorable prognosis. METHODS: We performed a systematic literature search on PUBMED and MEDLINE database from inception to December 5, 2021. Studies were analyzed based on predetermined eligibility criteria. RESULTS: A total of 57 studies containing 275 cases of COVID‐19 vaccine‐associated myocarditis were catalogued. Mean age was 26.7 years and male to female ratio was 14:1. For 86.9% of patients, myocarditis occurred after the second dose. Average time to onset and length of hospitalization were 3.7 and 3.9 days, respectively. Prognosis was largely benign, but there was a 1.1% reported mortality. Chest pain (95.2%), elevation of troponin (100%), and ST elevation on electrocardiography (68.5%) were common. Nonsteroidal anti‐inflammatory drugs (81.4%) were the most used medication, followed by colchicine (33.1%). CONCLUSIONS: Patients with COVID‐19 vaccine‐associated myocarditis are usually younger males presenting with chest pain 3–4 days after receiving their second dose of COVID vaccine. Diagnosis is made by exclusion of all other etiologies. Given significant population benefit from COVID‐19 vaccination, physicians should continue to encourage vaccination while remaining vigilant of the very rare occurrence of myocarditis following COVID‐19 vaccination.