Late last week, the U.S. Centers for Disease Control and Prevention (CDC) alerted health care professionals that they are monitoring the Vaccine Adverse Events Reporting System (VAERS) and the Vaccine Safety Datalink (VSD) for cases of young adults developing the rare heart-related complication myocarditis, after receiving a COVID-19 vaccine manufactured by Pfizer-BioNTech or Moderna. The COVID-19 Vaccine Safety Technical Work Group (VaST) of the CDC’s Advisory Committee on Immunization Practices (ACIP) is reviewing several dozen cases of myocarditis that have been reported in adolescents and young adults: more often in males rather than females; more frequently after the second dose rather than the first dose of either the Pfizer-BioNTech or Moderna vaccine; and typically appearing within 4 days of vaccination.