A Study to Learn About The COVID-19 (Study) Vaccine (Called COMIRNATY) in People That Are Less Than 21 Years Old.

The purpose of this clinical trial is to learn about the safety and effects of the study vaccine (called COMIRNATY) for the potential prevention of COVID-19. This study is seeking participants who:

1. Are age <21 years.
2. Have presentation to participating medical center with evaluation in Emergency Room and/or hospitalization.
3. Received either the 1st, 2nd, 3rd or booster dose(s) of COMIRNATY within 7 days of symptom onset.
4. Meet criteria of Centers for Disease Control and Prevention case definition of probable or confirmed myocarditis/pericarditis
5. Are capable of giving signed informed consent/assent (by parents/legal guardians of minors and/or patients), which includes compliance with the requirements and restrictions listed in the Informed Consent/Assent Document and in this protocol OR meets criteria for waiver of consent.

This study will examine the potential long-term effects associated with myocarditis/pericarditis following vaccination with COMIRNATY. The association of myocarditis/pericarditis in participants who received the study vaccine (COMIRNATY) compared with those associated with COVID-19 will also be examined. This will help us determine if COMIRNATY is safe and effective, and if there is a myocarditis/pericarditis association that should be noted. Participants will take part in this study for up to 5 years. During this time, they will receive complete cardiac imaging tests, and have follow up visits per guidance stated in the study protocol.

This is a low-interventional cohort study to determine cardiac and non-cardiac long-term outcomes of persons <21 years of age with myocarditis/pericarditis after the administration of COMIRNATY, compared with similarly aged persons with myocarditis/pericarditis associated with COVID-19, including MIS-C.

To be classified as having COMIRNATY-associated myocarditis/pericarditis, a person must 1) meet the CDC case definition for probable or confirmed myocarditis/pericarditis,15 2) have received any dose of COMIRNATY ≤ 7 days of symptom onset, and 3) have no other plausible alternative etiology at the time of enrollment. Inclusion criteria for participants are:

1. Age <21 years
2. Presentation to a participating medical center with evaluation in Emergency Room and/or hospitalization
3. Received either the 1st, 2nd, 3rd or booster dose(s) of COMIRNATY ≤7 days of symptom onset, even if a different brand of COVID-19 vaccine had been administered in earlier vaccinations Retrospectively ascertained participants must be enrolled within 2 years of diagnosis
4. COVID-19 related disease
5. Probable or confirmed myocarditis/pericarditis as per the contemporaneous CDC case definition at the time of diagnosis
6. Capable of giving signed informed consent/assent (by parents/legal guardians of minors and/or patients), which includes compliance with the requirements and restrictions listed in the Informed Consent/Assent Document and in this protocol OR meets criteria for waiver of consent.

To be classified as having myocarditis/pericarditis associated with COVID-19, a person must have 1) either acute severe COVID-19 infection or MIS-C, as defined by the CDC, 2) findings of probable or confirmed myocarditis in the CDC definition, 3) no other plausible alternative etiology.

Participants in all cohorts will be those who present to participating medical centers for care. This study is a collaboration between the National Heart, Lung, and Blood Institute (NHLBI)’s Pediatric Heart Network (PHN) and Pfizer.

Approximately 300 prospectively ascertained cases of children, adolescents, and young adults <21 years of age who receive care at participating medical centers for myocarditis/pericarditis associated with COMIRNATY, up to 200 retrospectively ascertained cases of persons <21 years of age who receive care for myocarditis/pericarditis associated with COMIRNATY, and approximately 100 persons <21 years of age with COVID-associated myocarditis/pericarditis, including MIS-C will be enrolled.