A higher-than-usual number of cases of a type of heart inflammation has been reported following Covid-19 vaccination, especially among young men following their second dose of an mRNA vaccine, according to the Centers for Disease Control and Prevention.
Dr. Cody Meissner, chief of pediatric infectious diseases at the Tufts Children’s Hospital in Boston, said “it is hard to deny that there’s some event that seems to be occurring in terms of myocarditis.”
William Schaffner, MD, an infectious diseases specialist from Vanderbilt University in Nashville, thinks certain characteristics are pointing toward a “rare, but real” signal. First, the events are clustering, occurring within days of vaccination. Second, they tend to be more common in males and younger people. Third, he says, the number of events is above the so-called “background rate”— the cases that could be expected in this age group even without vaccination.
Overall, 226 cases of myocarditis or pericarditis after vaccination in people younger than age 30 have been confirmed, Dr. Tom Shimabukuro, deputy director of the CDC’s Immunization Safety Office, said during a presentation to a Food and Drug Administration advisory group. Further investigation is needed, however, to confirm whether the vaccination was the cause of the heart problem.
The vaccines linked to the events are the mRNA vaccines made by Pfizer and Moderna. The only vaccine currently authorized for use in adolescents is made by Pfizer.
Teenagers and people in their early 20s accounted for more than half of the myocarditis cases reported to the CDC’s safety monitoring systems following Covid-19 vaccination, despite representing a fraction of people who have received the shot.