The United States’ Food and Drug Administration said in an internal memo that at least 10 children had likely died “because of” Covid-19 vaccinations, citing myocarditis, or heart inflammation, as a possible cause, the New York Times reported on Friday.

The Department of Health and Human Services, which includes the FDA, did not immediately respond to a Reuters request for comment on the report outside business hours.

Health Secretary Robert F Kennedy Jr has sharply changed government policy on Covid vaccines, limiting access to them to people 65 and older, as well as those with underlying conditions.

Kennedy, a longtime anti-vaccine crusader before taking on the nation’s top health post under President Donald Trump, has also linked vaccines to autism and sought to rewrite the country’s immunisation policies.

During Trump’s first term, when the pandemic erupted, and under his successor Joe Biden, US health officials strongly endorsed the vaccines as lifesaving.

The memo, written by the FDA’s chief medical and scientific officer, Vinay Prasad, did not disclose the ages or health conditions of the children, or the vaccine manufacturers involved, the New York Times said.

Prasad was quoted as calling the finding “a profound revelation” and announcing plans to tighten vaccine oversight, including requiring randomised studies for all subgroups.

The findings of the new FDA review have not been published in a peer-reviewed medical journal, the Times reported, adding that the Centres for Disease Control and Prevention’s vaccine committee is to meet next week.

Prasad, an oncologist who was a fierce critic of US Covid vaccine and mask mandates, regained his role as the FDA’s chief medical and scientific officer in September.

He advises the FDA commissioner and other senior officials on emerging medical and scientific issues impacting regulatory science and public health.