FDA to add heart risk warning to mRNA vaccines

WASHINGTON • The US Food and Drug Administration (FDA) has said it plans to move quickly to add a warning about rare cases of heart inflammation in adolescents and young adults to factsheets for the Pfizer-BioNTech and Moderna Covid-19 vaccines.

US Centres for Disease Control and Prevention (CDC) advisory groups found the inflammation in adolescents and young adults likely linked to the vaccines, but that the shots' benefits seemed to outweigh the risk.

Health regulators in several countries have been investigating whether the Pfizer-BioNTech and Moderna shots using the new mRNA technology present a risk and, if so, how serious.

In Singapore, six people were reported to have myocarditis, or inflammation of the heart muscle, and pericarditis, inflammation of the heart's outer lining, after getting an mRNA vaccine. Four of them are men aged under 30. The other two are a man and a woman, both aged above 40.

The two shots used in Singapore's national vaccination drive are Pfizer-BioNTech and Moderna - both mRNA vaccines.

The authorities said most of the cases had occurred within a few days after the second dose of the vaccine was given, and that all have recovered or been discharged well from hospital.

Three independent bodies of medical experts in Singapore have reiterated that the risk of heart conditions associated with the mRNA vaccines is very small, and have recommended that people still receive the vaccines in the interest of public health. As a precaution, vaccinated people, especially adolescents and younger men, are advised to avoid strenuous physical activity for one week after their second dose.

Similarly, the US Department of Health and Human Services, joined by leading doctor groups and public health officials in the country, have said the vaccines are safe and effective, and that the side effect affecting the heart is extremely rare.

Doctors and hospitals have been warned by the CDC to look out for symptoms of myocarditis or pericarditis, and the FDA warning will further raise awareness.

Dr Tom Shimabukuro, deputy director of the CDC's Immunisation Safety Office, said data from its monitoring systems suggests a rate of 12.6 cases per million in the three weeks after the second shot in those aged 12 to 39.

"We are observing this in the younger age groups, mainly in people in their teens and early 20s, and observing it more in males," he said. "This effect largely kind of disappears once you get into these older age groups - 50 and over."

The US Vaccine Adverse Event Reporting System recorded 347 observed cases of heart inflammation in the week after the second vaccine dose in males aged 12 to 24. Pfizer, whose vaccine has been authorised for use in Americans as young as 12 years old, previously said it had not observed a higher rate of heart inflammation than would normally be expected in the general population. Moderna said it is aware of such reports and is working with the public health and regulatory authorities to assess the issue.

REUTERS