. FDA announced it would add the warning after the Centers for Disease Control and Prevention (CDC) reported more cases of heart inflammation—either myocarditis or pericarditis—were found in young adults and children after they received the vaccines, which use mRNA technology..Will add revisions to its patient and provider fact sheets about “increased risks of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart) following vaccination” using Pfizer or Moderna COVID-19 shots...