Myocarditis Associated with COVID-19 Vaccination

Abstract

Myocarditis after the COVID-19 vaccine is one of the important adverse events following immunization, observed mainly after mRNA-based vaccines. Importantly, post-vaccination myocarditis was less common than myocarditis after SARS-CoV-2 infection, as it was scored at 19.7 per 1,000,000 doses and 2.76 per 1000 infections. Predominantly, its course was benign and, compared with the myocarditis after COVID-19 infection, significantly fewer patients developed heart failure or died among patients with post-vaccination myocarditis. The group at highest risk of myocarditis related to COVID-19 vaccination were young males who received a second dose of an mRNA vaccine. It was observed that, among mRNA vaccines, specifically mRNA-1273 was associated with a higher risk of myocarditis. The mechanism underlying myocarditis after COVID-19 vaccination is still under investigation and certain processes are being considered. Currently, some follow-up assessments of patients who developed vaccine-induced myocarditis are available and suggest a favorable prognosis. The aim of this review is to discuss the most recent data on myocarditis after COVID-19 vaccination considering its epidemiology, clinical presentation, diagnosis, management, relative risk of myocarditis compared with SARS-CoV-2 infection, potential underlying mechanism, and follow-up data of patients who developed post-vaccination myocarditis.

Keywords: 2019-nCoV vaccine mRNA-1273; COVID-19; COVID-19 vaccines; mRNA vaccines; myocarditis.

Figure 1

The summary of post-vaccination myocarditis-specific features. High-risk populations include males, young individuals under 30/40 years of age, and mainly those after the second dose of mRNA vaccine [9,27,30,58]. The mean time to symptoms occurrence after administration of the second dose of mRNA vaccine is 3.5 days and, in the majority of cases, symptoms resolve within 6 days [27,28,54]. Vaccine-induced myocarditis has a more benign course compared to myocarditis after SARS-CoV-2 infection [10].

Figure 2

The potential mechanisms underlying myocarditis after COVID-19 vaccination are associated with higher levels of androgens, hypersensitivity reactions, and molecular mimicry [9,21,30,83,85,86]. Higher levels of androgens among young males may enhance pro-inflammatory responses by enhanced Th1 lymphocyte reaction and cytokine production, and hypersensitivity reactions may be induced by mRNA, spike protein, LNPs, or vaccine adjuvants [9,21,30,83,85,86]. Molecular mimicry is associated with a cross-reaction of antibodies against spike protein with self-antigens such as myosin heavy chains or troponin C1 [91].