The Centers for Disease Control and Prevention (CDC) and its partners are investigating reports of myocarditis and pericarditis, two heart conditions, following mRNA COVID-19 vaccination. The CDC asks all clinicians to report cases using the Vaccine Adverse Event Reporting System. Reported cases have occurred predominantly young adults 16 years of age and older who have received the Pfizer-BioNTech or Moderna vaccine. In most cases, patients who presented for medical care responded well to medications and rest and had prompt improvement of symptoms. The CDC continues to recommend COVID-19 vaccination for everyone 12 years of age and older.