WASHINGTON, Dec 2, 2025 (BSS/AFP) - Vaccine makers saw their shares fall Monday on the New York Stock Exchange following the leak of a document attributed to a senior US official calling for a major overhaul of the country's vaccine-approval process.

The memo -- circulated by US media outlets last week and authored by Vinay Prasad, a senior official at the Food and Drug Administration (FDA) -- urged a substantial tightening of existing procedures and raised serious questions about the safety of Covid-19 vaccines.

Prasad, a hematologist-oncologist and health researcher appointed under the Trump administration, claimed the vaccines are linked to the deaths of at least 10 children, citing an unpublished internal analysis.

But Paul Offit, a US pediatric infectious-disease specialist, urged extreme caution.

"He makes a sensational and frightening statement that this vaccine may kill children, and then doesn't provide any evidence that is in support of that," Offit told AFP.

"The way this normally works is that you write up your case reports, you submit it to a medical journal, it goes through a peer review of experts, and then if they think that you have supported your claim that, in this case, the vaccine killed children, then it gets published."

On the basis of that analysis, Prasad says he wants to revisit vaccine-approval procedures, particularly for flu vaccines, and order additional studies in certain cases.

Stocks in Moderna, the biotech company responsible for a leading Covid vaccine, fell by around 6.8 percent in afternoon trading to $23.22. Novavax dropped more than 4.0 percent and Pfizer lost 1.8 percent.

The leak comes amid growing criticism of what many describe as the increasing politicization of federal health agencies by Donald Trump's administration.

Under Health Secretary Robert Kennedy Jr., known for his anti-vaccine views, the government has reshaped these agencies, carrying out mass layoffs and appointing polarizing figures to senior roles.

The Department of Health and Human Services and the FDA did not immediately respond to AFP requests for comment.