The US health regulator is investigating deaths potentially related to COVID-19 vaccines across multiple age groups as part of a safety review, a spokesperson for the Department of Health and Human Services said on Tuesday.

The HHS did not immediately clarify what age groups will be included in the FDA probe.

The US Food and Drug Administration Commissioner Marty Makary had previously said they were looking at such deaths in young people.

Last month, the agency's chief medical and scientific officer Vinay Prasad had told staffers in a memo that COVID shots probably contributed to the deaths of at least 10 children who died of heart inflammation and announced plans to tighten vaccine oversight.

The memo did not disclose the health conditions of the children, or the vaccine manufacturers involved. The findings, which have not been published in a peer-reviewed medical journal, were based on an initial analysis of 96 deaths between 2021 and 2024.

Moderna reiterated its previous statement that there were no new or undisclosed safety concerns in children or in pregnant women related to its mRNA-based COVID shot Spikevax.

Pfizer, which markets another mRNA-based COVID shot with partner BioNTech, also reaffirmed its safety and efficacy.

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

Kennedy, a longtime vaccine skeptic, has made far-reaching changes to the U.S. vaccine policy, which include dropping a long-standing recommendation for the hepatitis B birth dose, cutting funding for mRNA vaccines and, contrary to established science, linking vaccines to autism.