The FDA is requiring COVID vaccine makers Pfizer and Moderna to update their warnings about the possible risk of myocarditis and pericarditis.

Infectious disease experts say mRNA vaccines have been studied for decades, they are safe and effective, and were instrumental in saving lives during the COVID pandemic.

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.

This week, mRNA vaccines are set to face intense scrutiny from critics in Congress. Here's an explainer of how we know they are safe and effective.

The Food and Drug Administration says it has decided to continue approving COVID-19 vaccine updates for seniors and others at higher risk of severe disease, but will require vaccine makers to conduct major new clinical trials before approving them for wider use.

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 FDA’s recent activities regarding Covid-19 vaccines stray far from the well-established standards of vaccine regulatory processes.

The FDA will encourage new clinical trials on the widely used vaccines before approving them for children and healthy adults. The requirements could cost drugmakers tens of millions of dollars and are likely to leave boosters largely out of reach for hundreds of millions of Americans this fall.