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Association of Myocarditis With BNT162b2 Messenger RNA COVID-19 Vaccine in a Case Series of Children

Educational Objective
To identify the key insights or developments described in this article
Key Points

Question  What are the findings on cardiac imaging in children with myocarditis after COVID-19 vaccination?

Findings  In this case series of 15 children who were hospitalized with myocarditis after receipt of the BNT162b2 messenger RNA COVID-19 vaccine for 1 to 5 days, boys were most often affected after the second vaccine dose, 3 patients had ventricular systolic dysfunction, and 12 patients had late gadolinium enhancement on cardiac magnetic resonance imaging. There was no mortality, and all but 1 patient had normal echocardiogram results on follow-up 1 to 13 days after discharge.

Meaning  COVID-19 vaccine-associated myocarditis may have a benign short-term course in children; however, the long-term risks remain unknown.


Importance  The BNT162b2 (Pfizer-BioNTech) messenger RNA COVID-19 vaccine was authorized on May 10, 2021, for emergency use in children aged 12 years and older. Initial reports showed that the vaccine was well tolerated without serious adverse events; however, cases of myocarditis have been reported since approval.

Objective  To review results of comprehensive cardiac imaging in children with myocarditis after COVID-19 vaccine.

Design, Setting, and Participants  This study was a case series of children younger than 19 years hospitalized with myocarditis within 30 days of BNT162b2 messenger RNA COVID-19 vaccine. The setting was a single-center pediatric referral facility, and admissions occurred between May 1 and July 15, 2021.

Main Outcomes and Measures  All patients underwent cardiac evaluation including an electrocardiogram, echocardiogram, and cardiac magnetic resonance imaging.

Results  Fifteen patients (14 male patients [93%]; median age, 15 years [range, 12-18 years]) were hospitalized for management of myocarditis after receiving the BNT162b2 (Pfizer) vaccine. Symptoms started 1 to 6 days after receipt of the vaccine and included chest pain in 15 patients (100%), fever in 10 patients (67%), myalgia in 8 patients (53%), and headache in 6 patients (40%). Troponin levels were elevated in all patients at admission (median, 0.25 ng/mL [range, 0.08-3.15 ng/mL]) and peaked 0.1 to 2.3 days after admission. By echocardiographic examination, decreased left ventricular (LV) ejection fraction (EF) was present in 3 patients (20%), and abnormal global longitudinal or circumferential strain was present in 5 patients (33%). No patient had a pericardial effusion. Cardiac magnetic resonance imaging findings were consistent with myocarditis in 13 patients (87%) including late gadolinium enhancement in 12 patients (80%), regional hyperintensity on T2-weighted imaging in 2 patients (13%), elevated extracellular volume fraction in 3 patients (20%), and elevated LV global native T1 in 2 patients (20%). No patient required intensive care unit admission, and median hospital length of stay was 2 days (range 1-5). At follow-up 1 to 13 days after hospital discharge, 11 patients (73%) had resolution of symptoms. One patient (7%) had persistent borderline low LV systolic function on echocardiogram (EF 54%). Troponin levels remained mildly elevated in 3 patients (20%). One patient (7%) had nonsustained ventricular tachycardia on ambulatory monitor.

Conclusions and Relevance  In this small case series study, myocarditis was diagnosed in children after COVID-19 vaccination, most commonly in boys after the second dose. In this case series, in short-term follow-up, patients were mildly affected. The long-term risks associated with postvaccination myocarditis remain unknown. Larger studies with longer follow-up are needed to inform recommendations for COVID-19 vaccination in this population.

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Article Information

Accepted for Publication: July 20, 2021.

Published Online: August 10, 2021. doi:10.1001/jamacardio.2021.3471

Corresponding Author: Audrey Dionne, MD, Department of Cardiology, Boston Children's Hospital, 300 Longwood Ave, Boston, MA 02115 (audrey.dionne@cardio.chboston.org).

Author Contributions: Dr Dionne had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Dionne, Baker, Prakash, Saleeb, Newburger, Friedman.

Acquisition, analysis, or interpretation of data: Dionne, Sperotto, Chamberlain, Baker, Powell, Castellanos, De Ferranti, Newburger, Friedman.

Drafting of the manuscript: Dionne, Prakash, Friedman.

Critical revision of the manuscript for important intellectual content: Dionne, Sperotto, Chamberlain, Baker, Powell, Castellanos, Saleeb, De Ferranti, Newburger, Friedman.

Statistical analysis: Dionne, Sperotto.

Administrative, technical, or material support: Chamberlain, Baker, Castellanos, Saleeb, Friedman.

Supervision: Baker, Prakash, Newburger, Friedman.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was funded by the McCance Foundation (JWN).

Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Food and Drug Administration. Emergency Use Authorization letter for Pfizer-BioNTech COVID-19 Vaccine. May 10, 2021. Accessed July 1, 2021. https://www.fda.gov/media/144412/download
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