COVID-19 Resource Center

COVID-19 Resource Center

Perspective from Mariska S. Kemna, MD
Disclosures: Newburger and Truong report consulting for Pfizer. One other author reports receiving research grants from Genentech and the NIH. The other authors report no relevant financial disclosures.
December 06, 2021
3 min read

Symptoms of vaccine-related myocarditis in young people mild, resolve quickly

Perspective from Mariska S. Kemna, MD
Disclosures: Newburger and Truong report consulting for Pfizer. One other author reports receiving research grants from Genentech and the NIH. The other authors report no relevant financial disclosures.
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Most young people under the age of 21 years with suspected myocarditis following COVID-19 vaccination had mild symptoms that resolved quickly, according to data published in Circulation.

Most cases of suspected COVID-19 vaccine myocarditis occurred in white males and followed a messenger RNA (mRNA) vaccine, the researchers reported.

Graphical depiction of data presented in article
Data were derived from Truong DT, et al. Circulation. 2021;doi:10.1161/CIRCULATIONAHA.121.056583.

“The highest rates of myocarditis following COVID-19 vaccination have been reported among adolescent and young adult males. Past research shows this rare side effect to be associated with some other vaccines, most notably the smallpox vaccine,” Jane W. Newburger, MD, MPH, FAHA, associate chair of academic affairs in the department of cardiology at Boston Children’s Hospital, the Commonwealth Professor of Pediatrics at Harvard Medical School, and member of the American Heart Association Council on Lifelong Congenital Heart Disease and Heart Health in the Young, said in a press release issued by the AHA. “While current data on symptoms, case severity and short-term outcomes is limited, we set out to examine a large group of suspected cases of this heart condition as it relates to the COVID-19 vaccine in teens and adults younger than 21 in North America.”

The retrospective analysis included 139 adolescents and young adults aged younger than 21 years with 140 episodes of suspected myocarditis within 30 days of COVID-19 vaccination who presented to 26 U.S. centers before July 4, 2021. Myocarditis was classified as confirmed (n = 49) or probable (n = 91) based on CDC definitions.

Patient characteristics

Most patients with suspected myocarditis were male (90.6%) and white (66.2%). The median age was 15.8 years, according to the results.

Among those with suspected myocarditis, 97.8% had their case occur after a dose of any mRNA vaccine and 94.2% had theirs occur after a dose of the Pfizer/BioNTech vaccine.

More than 91% of cases reported occurred after the second vaccine dose, according to the results.

Characteristic of vaccine-related cardiac injury

Symptoms started at a median of 2 days after vaccination. The most common symptom was chest pain, in 99.3%, the researchers reported.

Treatments for suspected myocarditis included NSAIDs (81.3%), IV immunoglobulin (21.6%), glucocorticoids (21.6%), colchicine (7.9%) or no anti-inflammatory therapies (8.6%).

Researchers reported that the median hospital stay was 2 days.

According to the results, 18.7% of patients were admitted to the ICU, of whom two received inotropic/vasoactive support. None of the patients died or required extracorporeal membrane oxygenation support.

All patients had elevated troponin I (mean, 8.12 ng/mL) or troponin T (mean, 0.61 ng/mL).

Moreover, 69.8% of participants had abnormal ECGs and/or arrythmias and 18.7% had left ventricular ejection fraction of less than 55%. LV function had normalized among all participants at the time of follow-up, the researchers reported.

Ninety-seven patients underwent cardiac MRI at a median of 5 days from symptom onset. Among those patients, 77.3% had abnormal findings, including late gadolinium enhancement (76.3%) and myocardial edema (55.7%), and 50.5% met Lake Louise criteria.

“These data suggest that most cases of suspected COVID-19 vaccine-related myocarditis in people younger than 21 are mild and resolve quickly,” Dongngan T. Truong, MD, associate professor of pediatrics in the division of cardiology at the University of Utah and a pediatric cardiologist at Intermountain Primary Children’s Hospital, said in the release. “We were very happy to see that type of recovery. However, we are awaiting further studies to better understand the long-term outcomes of patients who have had COVID-19 vaccination-related myocarditis. We also need to study the risk factors and mechanisms for this rare complication.”

The researchers noted several limitations of the current case series, including a design that did not allow estimation of the incidence or risk for myocarditis in young people after vaccination or comparison of these risks with those following COVID-19 or MIS-C; its retrospective and descriptive nature design; and no reports of endomyocardial biopsy to rule out direct viral infection of the myocardium.

“It is important for health care professionals and the public to have information about early signs, symptoms and the time course of recovery of myocarditis, particularly as these vaccines become more widely available to children,” Truong said. “Studies to determine long-term outcomes in those who have had myocarditis after COVID-19 vaccination are also planned.”