The researchers suggest these findings could help improve safety and guide the development of future COVID vaccines.
Myocarditis is inflammation of the heart muscle caused by the body’s immune response to infection or, in rare cases, a vaccine. Symptoms of this heart condition include chest pain, shortness of breath, and fast heartbeats.
Although rare, myocarditis has occurred in people after receiving mRNA COVID-19 vaccines, most often after the second dose. According to the Vaccine Adverse Event Reporting System (VAERS) data, many individuals affected are young adults.
To investigate post-COVID vaccine myocarditis in this age group, scientists at Brigham and Women’s Hospital and Massachusetts General Hospital collected blood samples from 16 young adults hospitalized with myocarditis after receiving mRNA COVID-19 vaccines. They also analyzed blood samples from 45 vaccinated, healthy young people. The participants were between 12 and 21 years of age.
After analyzing the samples, the research team found that antibody profiling and T-cell responses in the young people who developed post-vaccine myocarditis were similar to vaccinated, healthy individuals.
However, the scientists discovered markedly elevated levels of full-length spike proteins in the plasma of those with post-vaccine myocarditis. In contrast, no free spike proteins were found in the healthy, vaccinated control participants. The researchers suggest that this indicates a unique immune response in individuals with post-vaccine heart inflammation.
In addition, the young people with myocarditis had higher blood levels of cytokines —an indication of inflammation, and troponin — an indicator of heart injury.
According to the study authors, although post-vaccine myocarditis generally occurs more commonly in males, this investigation found elevated spike proteins equally in males and females. Still, the scientists note that more research is needed to understand the mechanisms behind this rare vaccine complication.
“While this finding helps us better understand this potential complication, it does not alter the risk benefit ratio of receiving the COVID vaccines. The incidence of myocarditis and other heart-related complications among children infected with SARS-CoV-2 is much higher than the risk of post-vaccination myocarditis,” first author Lael Yonker, pediatric pulmonary medicine specialist at Mass General for Children, said in a news report.
The study appears in Circulation, a journal of the American Heart Association.