Myocarditis in Younger Men Following COVID-19 Vaccination Not Common, But Higher Than Expected

June 30, 2021

By Denise Baez

Myocarditis occurred in previously healthy military patients with similar clinical presentations following receipt of an mRNA coronavirus disease 2019 (COVID-19) vaccine, according to a study published in JAMA Cardiology.

“In this case series, we describe 23 patients with clinical evidence of myocarditis following mRNA COVID-19 vaccination and meeting the Centers for Disease Control and Prevention case definition for probable myocarditis,” wrote Jay Montgomery, MD, Defense Health Agency, Falls Church, Virginia, and colleagues.

Myocarditis was identified within 4 days of receipt of a COVID-19 vaccine. In 20 of the patients, the diagnosis was made after the second dose of mRNA COVID-19 vaccine; these episodes occurred against the backdrop of 2.8 million doses of mRNA COVID-19 vaccines administered.

“Myocarditis cases were small, but the number was higher than expected among male military members after a second vaccine dose,” the authors wrote. “Vigilance for rare adverse events, including myocarditis, after COVID-19 vaccination is warranted but should not diminish overall confidence in vaccination during the current pandemic.”

A total of 23 male patients (22 currently serving in the military and 1 retiree) presented with acute onset of marked chest pain within 4 days after receipt of an mRNA COVID-19 vaccine. All military members were previously healthy with a high level of fitness. Seven received Pfizer’s BioNTech mRNA vaccine and 16 received Moderna’s mRNA-1273 vaccine.

A total of 20 patients had symptom onset following the second dose of an appropriately spaced 2-dose series. All patients had significantly elevated cardiac troponin levels. Among 8 patients who underwent cardiac magnetic resonance imaging within the acute phase of illness, all had findings consistent with the clinical diagnosis of myocarditis. Additional testing did not identify other etiologies for myocarditis, including acute COVID-19 and other infections, ischaemic injury, or underlying autoimmune conditions.

All patients received brief supportive care and were recovered or recovering at the time of this report.

“Further surveillance and evaluation of this adverse event following immunisation is warranted,” the authors wrote. “It is important to frame concerns about potential vaccine-associated myocarditis within the context of the current pandemic. Infection with SARS-CoV-2 [severe acute respiratory syndrome coronavirus 2] is a clear cause of serious cardiac injury in many patients. The mechanism of injury may be direct infection, an immune-mediated response, or a combination of direct or indirect effects. Prevalence of cardiac injury may be as high as 60% in seriously ill patients. Notably, nearly 1% of highly fit athletes with mild COVID-19 infection have evidence of myocarditis on cardiac MRI. Given that COVID-19 vaccines are remarkably effective at preventing infection, any risk of rare adverse events following immunisation must be carefully weighed against the very substantial benefit of vaccination.”


SOURCE: JAMA Cardiology