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.