Newswise — New Haven, Conn. — Upon the initial administration of COVID-19 vaccines two years ago, there was a surge in myocarditis cases, which is the inflammation of the heart muscle, primarily among vaccinated young males receiving mRNA vaccines. The root cause of this response remained unknown.

Yale researchers have discovered the immune pattern associated with cases of cardiac inflammation in a recent investigation.

As reported in the May 5th issue of Science Immunology, the outcomes of this study exclude some of the speculated causes of myocarditis and offer potential strategies to further decrease the occurrence of this uncommon side effect of vaccination, according to the authors.

Myocarditis is typically a mild inflammation of the heart tissue that can result in scarring, but it generally resolves within a few days. The upsurge in myocarditis cases during vaccination was mostly observed in males aged in their late teens or early twenties who had received mRNA vaccines, which are formulated to prompt an immune response targeted specifically to the SARS-CoV-2 virus.

As per the Centers for Disease Control and Prevention (CDC), around 22 to 36 out of 100,000 males aged 12 to 17 experienced myocarditis within 21 days after getting their second dose of vaccine. In contrast, the occurrence of myocarditis was 50.1 to 64.9 cases per 100,000 among unvaccinated males in this age group after acquiring COVID-19 infection.

In the recent investigation, the Yale research group meticulously examined the immune system responses of vaccinated individuals who developed myocarditis. Carrie Lucas, an associate professor of immunobiology, Akiko Iwasaki, a Sterling Professor of Immunobiology, and Inci Yildirim, an associate professor of pediatrics and epidemiology, headed the team.

Their findings indicated that myocarditis was not induced by antibodies generated by the vaccine but instead by a more comprehensive immune response that involved inflammation and immune cells.

As Lucas explains, "In these individuals, their immune systems become excessively stimulated, leading to an excessive production of cytokine and cellular responses."

Prior research had proposed that extending the interval between vaccine doses from four to eight weeks might decrease the likelihood of developing myocarditis.

Lucas highlighted that the risk of myocarditis is much higher in unvaccinated individuals who contract the COVID-19 virus, as per the CDC's research, than in those who receive the vaccine. She emphasized that vaccination provides the most effective defense against COVID-19-induced illness.

Anis Barmada, an M.D./Ph.D. student at Yale School of Medicine and a co-first author of the paper, along with Jon Klein, who is also a Yale M.D./Ph.D. student, expressed hope that this new understanding would facilitate the optimization of mRNA vaccines. Barmada emphasized that mRNA vaccines offer significant health advantages during the pandemic and have immense potential for saving lives in various future applications.

Journal Link: Science Immunology