Reports of myocarditis, an inflammation of the heart muscle , have been noted in people who have received a messenger RNA vaccine such as those developed by Pfizer / BioNTech or  Moderna , noted the Centers for Disease Prevention and Control (CDC), the main federal public health agency in the country.

Most of them “appear to be benign,” they explained, saying they are monitoring the situation. “Relatively few” cases have been reported, according to the CDC, which did not specify the exact number or the ages of those affected. They were detected mainly in “adolescents and young adults”, in “four days after” the injection.

These myocarditis, which occur more often “after the second dose”, affect men more than women. The number of reported myocarditis does not currently exceed the normal rate in people in this age group, according to health authorities.