FDA tightens heart tox warnings on mRNA COVID vaccines

The FDA has instructed Pfizer and Moderna to add stronger warnings to the labels of their COVID-19 vaccines about the risk of cardiotoxicity in some patients, citing a recent study and new data.

While Pfizer/BioNTech's Comirnaty and Moderna's Spikevax products already include warnings about the risk of myocarditis and pericarditis, particularly in young men, the new wording extends the range of patients deemed to be at elevated risk.

For Comirnaty, the label warned of an elevated risk in the 12 to 17 age group, while for Spikevax, it covered those aged 18 to 24. Now, both shots will carry a warning spanning patients aged 16 to 25, which in part reflects the vanishingly reduced vaccination rate against COVID-19 in younger children.

Letters sent to both companies suggest the new wording will read: "Following administration of the 2023-2024 Formula of mRNA COVID-19 vaccines, the highest estimated incidence of myocarditis and/or pericarditis was in males 16 through 25 years of age," which the FDA said was an incidence of around 38 cases per million doses.

According to the CDC, cases of myocarditis and pericarditis are rare with the vaccines and, in most cases, resolve within a few days of dosing. None of the companies involved have commented on the change in the warning text.

Yesterday, a Senate hearing was held to discuss whether health officials "downplayed and hid" myocarditis and other adverse events associated with COVID-19 vaccines.

The label changes come amid increased scrutiny of vaccines in general and a tightening of the rules concerning COVID-19 shots by health officials in the Trump administration, who variously held views that ran counter to the prevailing consensus on immunisation policy against the virus, including recommendations on vaccine use in children, annual boosters, and the emergency authorisation of the shots.

Earlier this week, the FDA said it would introduce stricter rules on the approval of new vaccines, including a requirement for randomised, controlled trials for those intended for use in younger, otherwise healthy patients, while booster shots will be recommended for a narrower population of over-65s with underlying conditions that put them at elevated risk of COVID-19 complications.

Later today, the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) is scheduled to meet to discuss the coronavirus strain selection for boosters used in the coming season in the autumn.

Moderna pulls FDA filing for flu/COVID combo shot

Meanwhile, Moderna has withdrawn its marketing application in the US for its mRNA-1083 combination vaccine against influenza and COVID-19 in an acknowledgement that it will need to wait for efficacy data from a phase 3 trial before it secures approval.

The company had previously hinted that might be the case given the evolving regulatory framework for vaccines in the US and a decision by the FDA to push back a decision date for the application from November to early 2026. The company said it plans to resubmit the application later this year once the new data from the mRNA-1010 trial comes in, which is expected in the summer.