FDA adds warning of rare heart inflammation to Pfizer, Moderna vaccines

The U.S. Food and Drug Administration on Friday added a warning to patient and provider fact sheets for the Pfizer and Moderna Covid-19 vaccines to indicate a rare risk of heart inflammation.

For each vaccine, the fact sheets were revised to include a warning about myocarditis and pericarditis after the second dose and with the onset of symptoms within a few days after receiving the shot.

Myocarditis is the inflammation of the heart muscle and pericarditis is the inflammation of the tissue surrounding the heart. Health officials said the benefits of receiving the vaccine still outweigh any risk.

“The risk of myocarditis and pericarditis appears to be very low given the number of vaccine doses that have been administered,” Janet Woodcock, acting FDA commissioner, said in a statement.

“The benefits of Covid-19 vaccination continue to outweigh the risks, given the risk of Covid-19 diseases and related, potentially severe, complications,” she said.

The FDA update follows a review and discussion by the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices meeting on Wednesday. 

There have been more than 1,200 cases of a myocarditis or pericarditis mostly in people 30 and under who received the shots, according to presentation slides from the CDC meeting.

About 300 million shots had been administered as of June 11, according to the CDC. There have been just 12.6 heart inflammation cases per million doses for both vaccines combined.

— CNBC’s Berkeley Lovelace Jr. contributed reporting