Post-Vaccine Myocarditis: Clinical Insights and Epidemiological Trends

Abstract

Myocarditis is a rare but key adverse event linked to mRNA COVID-19 vaccines, predominantly in young males. Epidemiological data indicate an incidence of approximately 12.6 cases per million doses administered to patients aged 12-39 years, mostly following the second dose of the vaccine. Most patients present with elevated levels of cardiac biomarkers, chest pain, and abnormal ECG findings within a few days of vaccination. Proposed mechanisms for the exact pathophysiology of this include molecular mimicry between the SARS-CoV-2 spike protein and cardiac antigens, activation of immune pathways, and dysregulated cytokine expression. Despite these findings, the overall benefit-risk balance for COVID-19 vaccination remains positive, as the majority of patients recover fully. In contrast, COVID-19-associated myocarditis is more common and more severe, with an estimated incidence of 1,000-1,400 cases per 100,000 infections. Clinical presentation of vaccine-associated myocarditis is usually mild and self-limiting, and most patients do recover without significant long-term effects. Treatment is usually supportive in nature and has an emphasis on ruling out acute coronary syndrome and symptomatic management for heart failure or arrhythmias if present. Given its low incidence and the generally good outcome, vaccination against COVID-19 is recommended from 12 years of age and above, with provision for ongoing surveillance for monitoring and management of rare adverse events like myocarditis.