A CDC safety group said there's a "likely association" between a rare heart inflammatory condition in adolescents and young adults mostly after they've received their second Covid-19 vaccine shot, citing the most recent data available. There have been more than 1,200 cases of a myocarditis or pericarditis mostly in people 30 and under who received Pfizer's or Moderna's Covid vaccine, according to a series of slide presentations published Wednesday for a meeting of the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices. Myocarditis is the inflammation of the heart muscle, while pericarditis is the inflammation of the membrane surrounding the heart. The agency said there have been 267 cases of myocarditis or pericarditis reported after receiving one dose of the mRNA vaccines and 827 reported cases after two doses through June 11. Roughly 300 million of the shots had been administered as of June 11. Men under 30 make up the bulk of the cases, the CDC said. Of the 295 people who have developed the condition and have been discharged, 79% of them have fully recovered. Nine people were hospitalized, with two in intensive care as of June 11. The CDC is coordinating its investigation with the Food and Drug Administration, which last month authorized the Pfizer-BioNTech vaccine for adolescents ages 12 to 15. Symptoms, which include chest pain and shortness of breath, typically develop within a week of receiving the shot with most developing within four days, the agency said.