Data increasingly suggest that a causal link exists between COVID-19 mRNA vaccination and myocarditis in adolescents and young adult males. The risk of myocarditis appears highest after the second dose of mRNA vaccine, which has led officials in Hong Kong, Norway, Great Britain and other countries with lower rates of new infection than the United States to recommend a single dose of the Pfizer-BioNTech vaccine for children 12 and under, providing partial coverage while potentially reducing the risk seen with the second dose of vaccine. A pair of studies published earlier this month in The New England Journal of Medicine that examined the incidence rate of myocarditis following full vaccination in Israel demonstrate the potential risks of myocarditis. One study found that the incidence was highest among males aged 16 to 29 and the second found that boys between 16 and 19 had the highest incidence rate after the second dose, about nine times higher than their unvaccinated peers.
While these countries will revisit the single dose approach as more information becomes available, the U.S. has proceeded with full dosage. More than 63,000 children were hospitalized in the U.S. with COVID-19 from August 2020 to October 2021, and at least 520 have died. Some children have developed “long COVID”, in which symptoms can persist for months, and more than 4,000 have been diagnosed with multisystem inflammatory syndrome in children (MIS-C). Advisers to the CDC reviewed data on myocarditis and unanimously voted in June to recommend the vaccine for children ages 12 and older, saying the benefits far outweighed the risk. Public health experts maintain the disease is worse than possible side effects, like myocarditis, and believe such concerns should be part of the public discussion on vaccine dosage in children.
“We continue to work diligently to understand the true risk of myocarditis following mRNA COVID-19 vaccination,” said Dr. Buddy Creech, Director of the Vanderbilt Vaccine Research Program and President-Elect of PIDS. “CDC-based vaccine safety systems, such as the Vaccine Adverse Event Reporting System (VAERS), are capturing these events as they occur, at an estimated frequency of approximately 1 in 14,000 in males in the highest risk age groups in the US. Whether extending the interval between doses, or potentially using only one dose of vaccine, will be a successful strategy at reducing risk while maintaining the benefit of vaccination, remains unclear at this point.”