In a recent development, the U.S. Food and Drug Administration is reportedly planning to implement a “black box” warning for COVID-19 vaccines. This information comes from a CNN report on Friday, which cites two sources familiar with the agency’s intentions.

The specifics of this warning remain unclear. It is not yet determined whether it will be limited to mRNA vaccines or extended to all types of COVID vaccines. Additionally, the scope of the warning across different age groups has not been disclosed.

Black box warnings are prominently displayed at the top of drug prescribing information, serving as a crucial alert to health practitioners and patients about the most severe risks associated with a medication.

It’s the FDA’s most serious warning – intended to warn about risks, such as death or life-threatening disabling reactions that should be weighed against the benefits. 

A Department of Health and Human Services spokesperson told CNN that unless the agency announces a change, any reports about what it might do is “pure speculation.” 

The plan, which is expected to be unveiled before the end of the year, has not been finalized and may still change, CNN reports. 

Vinay Prasad, the FDA’s top vaccine regulator, is reportedly leading the potential change, CNN said. 

Earlier this month, a dozen prior leaders of FDA — appointed by Republicans and Democrats alike — issued a scathing denunciation of new FDA assertions casting doubt on vaccine safety after an internal memo by Prasad was leaked. 

Prasad’s memo claimed — without providing evidence — that COVID-19 vaccines caused 10 children’s deaths. It went on to outline planned agency changes in handling those and certain other vaccines, and said that FDA staff who disagreed should resign.

Among Prasad’s plans were revising how yearly flu shot updates are handled and focusing more on “the benefits and harms of giving multiple vaccines at the same time.” A common message of vaccine skeptics is that too many shots may overwhelm kids’ immune systems or that ingredients may build up to cause harm — although scientists say repeated research into those claims has turned up no concerns.

The former FDA leaders wrote that Prasad’s claim about child deaths related to COVID-19 vaccines had been reported to a surveillance system that doesn’t contain medical records or other information sufficient to prove a link — and that government scientists had carefully combed through those reports in previous years, reaching different conclusions. They also noted that “substantial evidence” shows COVID-19 vaccines reduce children’s risk of severe disease and hospitalization.

CNN Newsource and the Associated Press contributed to this report.