A higher-than-expected number of young men have experienced heart inflammation after their second dose of the mRNA COVID-19 shots from Pfizer/BioNTech and Moderna, according to data from two vaccine safety monitoring systems, the U.S. Centers for Disease Control and Prevention (CDC) said on Thursday.
The CDC and other health regulators have been investigating heart inflammation cases after Israel’s Health Ministry reported that it had found a likely link to the condition in young men who received Pfizer’s COVID-19 vaccine.
The agency said it is still assessing the risk from the condition and has not yet concluded that there was a causal relationship between the vaccines and cases of myocarditis or pericarditis.
While some patients required hospitalization, most have fully recovered from their symptoms, the CDC said.
About 130 million people in the United States have received both doses of one of the mRNA vaccines.