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 study is to learn about the safety and effects of the 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 any dose(s) of COMIRNATY within 21 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.