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 US 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.