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.