COVID-19 mRNA vaccination benefits outweigh the risk for myocarditis

Presented by

Prof. Biykem Bozkurt, Baylor College of Medicine Houston, USA

Conference

AHA 2021

COVID-19 mRNA vaccines are linked to an increased risk of myocarditis, especially in young males. However, the risk is small and mRNA vaccine-related myocarditis is predominantly mild and self-limited. The evidence to date shows that the benefits of vaccination outweigh the risks.

Prof. Biykem Bozkurt (Baylor College of Medicine Houston, TX, USA) discussed the evidence to date regarding COVID-19 vaccination and the occurrence of myocarditis [1]. Each year, 10–20 per 100,000 individuals are diagnosed with myocarditis, mostly affecting young males. Post-vaccination myocarditis has been reported as a rare event following smallpox, influenza, or other vaccinations [2].

Initial reports of myocarditis after COVID-19 mRNA vaccination demonstrated myocarditis rates of 1 in 100,000 vaccinated individuals [3]. The reported risk in young individuals (16–30 years) is higher, with approximately 1 case of myocarditis in 20,000 vaccinated individuals. Young males between 12 and 17 years appeared to have the highest risk of myocarditis after mRNA vaccination. Most cases occurred after administration of the second vaccine dose. Although most individuals needed hospitalisation, the symptoms were predominantly mild [2]. Notably, an analysis of data from the largest healthcare organisation in Israel found that the risk of acquiring myocarditis after vaccination (2.7/100,000) is smaller compared with the risk of SARS-CoV-2-related myocarditis (11/100,000) [4]. Moreover, other cardiac events, such as deep-vein thrombosis, myocardial infarction, pericarditis, and pulmonary embolism are increased in COVID-19. On 23 June 2021, the US Centers for Disease Control and Prevention (CDC) concluded that the benefits of vaccination outweigh the risks in all populations, including young males.

The suggested mechanisms underlying vaccine-related myocarditis include molecular mimicry between spike protein and self-antigens, a dysregulated immune response, auto-antibody production against cardiac proteins, and immunogenicity of RNA in certain individuals [2]. In clinical practice, most cases of post-vaccination myocarditis presented with chest pain 2–3 days after the second dose was administered. They did not show particular comorbidities or a history of COVID-19. Elevated cardiac troponin and CRP levels were observed in most patients. Furthermore, ECGs and cardiac MR were often abnormal. Physicians should consider using ECG, cardiac troponin measurement, and cardiac MR if an individual presents with chest pain after COVID-19 vaccination. The medical treatment of mild post-vaccination myocarditis cases includes non-steroidal anti-inflammatory drugs (NSAIDs), colchicine, steroids, and intravenous immunoglobulin [2].

In conclusion, the benefits of vaccination against SARS-CoV-2 outweigh the risks. Although there is a slightly increased risk of myocarditis after vaccination, especially in young males, the symptoms usually resolve in 4–5 days.

1. Bozkurt B. COVID-19 Vaccination and Cardiovascular Disease – Assessing the Evidence to Date. CS.ME.496, AHA 2021 Scientific Sessions, 13–15 November.
2. Bozkurt B, et al. Circulation. 2021;144(6):471–484.
3. Montgomery J, et al. JAMA Cardiol. 2021.
4. Barda N, et al. N Engl J Med. 2021;385:1078–1090.

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