Rate of Myocarditis in Vaccinated Boys Slightly Higher Than Thought, Israeli Study Finds January 26, 2022 Auto Bot Centers for Disease Control and Prevention, Coronavirus (2019-nCoV), Heart, Teenagers and Adolescence, Vaccination and Immunization 0 Myocarditis, or inflammation of the heart muscle, occurred in 1 of 12,361 boys between 12 and 15 years old within a week of receiving a second dose of the Pfizer-BioNTech vaccine, researchers found.