FILE PHOTO: A U.S. Food and Drug Administration (FDA) logo, a syringe and a vial are seen in this illustration taken May 13, 2025. REUTERS/Dado Ruvic/Illustration/File Photo

Dec 12 (Reuters) - The U.S. Food and Drug Administration intends to put a "black box" warning on COVID-19 vaccines, CNN reported on Friday, citing two people familiar with the agency's plans.

The warning is the most serious type and highlights major risks such as severe side effects and restrictions.

The plan to include the warnings for COVID shots is being orchestrated by Vinay Prasad, the FDA's chief medical and scientific officer and director of the agency's Center for Biologics Evaluation and Research, according to the report.

"Unless the FDA announces it, any claim about what it will do is pure speculation," U.S. Department of Health and Human Services spokesperson Andrew Nixon said about the plans to include the warning.

Following the CNN report, vaccine maker Moderna pointed to a statement it issued in September about the safety of its COVID shot. Pfizer also reiterated a statement that its vaccine continues to demonstrate a favorable safety and efficacy profile supported by extensive real-world evidence.

Last month, Prasad told staffers in a memo that COVID shots probably contributed to the deaths of at least 10 children who died of heart inflammation.

The FDA is investigating deaths potentially related to COVID-19 vaccines across multiple age groups as part of a safety review, a HHS spokesperson said on Tuesday.

FDA Commissioner Marty Makary has previously said the agency was looking at such deaths in young people.

Health Secretary Robert F. Kennedy Jr., a long time vaccine skeptic, has sharply changed government policy on COVID vaccines, limiting access to people aged 65 and above, as well as those with underlying conditions.

The plan to add the warning has not been finalized and may still change, CNN reported.

It was not immediately clear whether the plans for the warnings, expected to be unveiled by the end of the year, would be applied only to mRNA vaccines or all COVID vaccines, and if they would apply to all age groups, the report added.

Vaccines from Pfizer and partner BioNTech and Moderna use messenger RNA technology, while Novavax's shot is a more traditional protein-based one.

(Reporting by Sriparna Roy in Bengaluru; Editing by Arun Koyyur and Shinjini Ganguli)