The updated warnings highlight a rare risk of heart inflammation in teen boys and young men, CBS News reported. The warning applies to males ages 16 to 25 and is based on new data from FDA safety monitoring and a 2023 study. This includes both Pfizer's Comirnaty and Moderna's Spikevax vaccines.

The US Food and Drug Administration will now require Covid-19 vaccines from Pfizer/BioNTech and Moderna to use expanded warning labels with more information about the risk of a rare heart condition after vaccination.

In another sign of growing scrutiny over Covid-19 vaccines, the Food and Drug Administration has asked the two makers of mRNA vaccines to widen the age range of boys and young men that their labels say are at risk for a rare side effect causing heart inflammation.