Myocarditis in Adolescents After COVID-19 Vaccine Typically Mild

Megan Brooks

August 10, 2021

Adolescents can develop mild myocarditis as a rare complication after COVID-19 vaccination, as has been reported in adults, an early case series from Boston confirms.

The adolescents who developed heart inflammation after vaccination typically had a benign course, with symptoms resolving without treatment, although one patient had persistent borderline low left ventricular (LV) function, report Audrey Dionne, MD, and colleagues at Boston Children's Hospital.

"Despite the risks of myocarditis associated with vaccination, the benefits of vaccination likely outweigh risks in children and adolescents," they say.

They estimate that for males 12 to 29 years of age, COVID-19 vaccination prevents 11,000 COVID-19 cases, 560 hospitalizations, 138 intensive care unit admissions, and six deaths, compared with 39 to 47 expected myocarditis cases.

The case series was published online August 10 in JAMA Cardiology.

Long-term Risks Unknown 

Dionne and colleagues reviewed the results of comprehensive cardiac imaging in 14 boys and one girl, 12 to 18 years years of age (median, 15 years), who were hospitalized with myocarditis after receiving the Pfizer-BioNTech messenger RNA COVID-19 vaccine.

Symptoms started 1 to 6 days after vaccine administration (most after the second dose) and included chest pain in all 15 patients, fever in 10 (67%), myalgia in eight (53%), and headache in six (40%).

On admission, all patients had elevated troponin levels (median, 0.25 ng/mL; range, 0.08 - 3.15 ng/mL). Troponin levels peaked 0.1 to 2.3 days after admission.

Echocardiography revealed decreased LV ejection fraction (EF) in three patients (20%) and abnormal global longitudinal or circumferential strain in five patients (33%). No patient had a pericardial effusion.

Cardiac MRI findings were consistent with myocarditis in 13 patients (87%), including late gadolinium enhancement in 12 (80%), regional hyperintensity on T2-weighted imaging in two (13%), elevated extracellular volume fraction in three (20%), and elevated LV global native T1 in two (20%).

The patients remained in the hospital for 1 to 5 days (median, 2 days) and were discharged. No patient required admission to the intensive care unit.

In follow-up assessments performed 1 to 13 days after hospital discharge, symptoms of myocarditis had resolved in 11 patients (73%).

One patient (7%) had persistent borderline low LV systolic function on echocardiogram (LVEF, 54%).

Troponin levels remained mildly elevated in three patients (20%). One patient (7%) had nonsustained ventricular tachycardia on ambulatory monitor.

The authors say longitudinal studies of patients with myocarditis after COVID-19 vaccine "will be important to better understand long-term risks."

In a statement from the UK nonprofit Science Media Centre, Peter Openshaw, FMedSci, Imperial College London, says: "The problem with case series of this type is the lack of comparison groups. How many cases of myocarditis might be seen in normal children, or those given other vaccines (including those that are not for COVID), or in teenagers infected with SARS-CoV-2?"

"As the authors note, myocarditis does happen after other vaccines. The estimated rate (62.8 cases per million) makes this a rare event," Openshaw says.

"My view that teenagers should be considered for vaccination is not changed by this new publication," he adds.

This study was funded by the McCance Foundation. The authors have declared no relevant conflicts of interest. Openshaw has served on scientific advisory boards for Janssen/J&J, Oxford Immunotech, GSK, Nestle, and Pfizer in relation to immunity to viruses (fees paid to Imperial College London).

JAMA Cardiol. Published online August 10, 2021. Full text

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