A team led by researchers from the Centers for Disease Control and Prevention (CDC) found that many patients under age 30 who developed myocarditis after receiving a vaccination against COVID-19 also showed abnormal cardiac MRI results. Authors of a study published in the Journal of the American Medical Association sought to describe reports of myocarditis and the reporting rates after mRNA-based COVID-19 vaccination in the U.S. (2022; doi:10.1001/jama.2021.24110).
To that end, the CDC began tracking adverse events, including myocarditis and pericarditis, among individuals who had been vaccinated. Myocarditis is an inflammatory condition of the heart muscle that has a bimodal peak incidence during infancy and adolescence or young adulthood.
The research team used Vaccine Adverse Event Reporting System (VAERS) data from December 2020 to August 2021, including information from more than 192 million Americans older than 12 years old who had gotten either the Pfizer or Moderna COVID-19 vaccine. The authors compared actual myocarditis rates found in the VAERS data to expected rates-calculated by 2017-2019 insurance claims data-by age and sex of the patients.
For individuals younger than 30 years of age, medical record reviews and clinician interviews were conducted to describe clinical presentation, diagnostic test results, treatment, and early outcomes. Among the 192.4 million Americans who received a coronavirus vaccine, there were 1,626 reports of myocarditis. The median age of those reporting the condition was 21, with median symptom onset coming 2 days after vaccination. More than 80 percent of myocarditis cases were males.
Cases of myocarditis shown within 7 days after COVID-19 vaccination exceeded the expected rates of the condition across multiple age and sex strata. Myocarditis numbers were highest after the second vaccination dose in adolescent men ages 12-15 years, 16-17 years, and 18-24 years. A total of 826 myocarditis cases were found among individuals younger than 30 years of age who had detailed clinical information available.
Of these cases, 792 of 809 (98%) had elevated troponin levels, while 569 of 794 (72%) had abnormal electrocardiogram results. In addition, 223 of 312 (72%) had abnormal cardiac MRI results. Approximately 96 percent of patients (784/813) were hospitalized and 87 percent of these study participants had resolution of presenting symptoms by hospital discharge. Nonsteroidal anti-inflammatory drugs were the most common treatment.
"Based on passive surveillance reporting in the U.S., the risk of myocarditis after receiving mRNA-based COVID-19 vaccines was increased across multiple age and sex strata and was highest after the second vaccination dose in adolescent males and young men. This risk should be considered in the context of the benefits of COVID-19 vaccination," the authors wrote.
"Since vaccinating young adults and teenagers, we've seen rare cases of heart inflammation (myocarditis and pericarditis) among mostly males, typically after the second dose of vaccine," noted C. Buddy Creech, MD, MPH, FPIDS, Director of the Vanderbilt University Medical Center (VUMC) Vaccine Research Program, and a co-author of the study.
"It's important when we see possible vaccine side effects that we understand why it's happening, how to avoid it and how best to manage it," said Creech, who is also the Edie Carell Johnson Chair and Professor in the Division of Pediatric Infectious Diseases at VUMC.
He also addressed the finding that more than 70 percent of patients younger than 30 who developed myocarditis after receiving a COVID-19 vaccine also had abnormal cardiac MRI results.
"I think the way to think about this is to say that cardiac MRI is the most sensitive way to capture myocarditis in patients with suspected myocarditis," Creech explained. "EKG and echocardiogram are important, but mild cases may be missed unless cardiac MRI is also performed. In addition, cardiac MRI gives more information about the nature and location of the inflammation."
Noting the safety and effectiveness of COVID-19 vaccines, the study results could prove useful in gaining a better understanding of the benefits of COVID-19 vaccines and the connection between vaccinations and myocarditis, he noted.
"Moreover, there may be options for young males that would reduce the risk of myocarditis," he concluded," such as spacing the two doses of vaccine to 8-12 weeks [apart], that need to be studied further."
Mark McGraw is a contributing writer.