The U.S. Food and Drug Administration has added warnings about the rare risk of heart inflammation linked to the two-dose Pfizer-BioNTech and Moderna COVID-19 vaccines.
The agency said Friday evening that it revised patient and provider fact sheets for the vaccines to include warnings about an increased risk of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart) after vaccination.
The risk of inflammation seems to increase particularly after the second dose, with onset of symptoms within a few days after vaccination, the FDA said, citing reports of adverse events.
Among people ages 30 and younger who received a COVID-19 vaccine, 616 reports of myocarditis and pericarditis have been submitted to the Vaccine Adverse Event Reporting System, a national surveillance program, as of June 21. Federal health regulators have confirmed 393 reports of inflammation, according to the Centers for Disease Control and Prevention.
More than 300 million COVID-19 vaccine doses were administered in the U.S. by that date.
Most cases of heart inflammation have been reported after receiving either a Pfizer or Moderna mRNA COVID-19 vaccine. The cases appear to be higher in males and found in the week after the second dose, Reuters reported.
Health regulators in several countries have been investigating cases of pericarditis and myocarditis following vaccination with the Pfizer or Moderna shots, reported the news agency.
The addition of the warnings comes after an extensive review of information and discussion by the CDC’s Advisory Committee on Immunization Practices meeting on Wednesday.
The Pfizer and Moderna vaccine fact sheets note that recipients should immediately seek medical attention if they experience chest pain, shortness of breath or a fast-beating, fluttering or pounding heart after vaccination.