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.

This observational study will determine the spectrum and time course of coronary artery involvement, left ventricular (LV) systolic function, and arrhythmias or conduction system disturbances within the first year from illness onset, and to define associated clinical and laboratory factors in a cohort of MIS-C affected patients.