FDA Plans to Review Already Approved RSV Immunizations

Federal agencies have spoken to pharmaceutical companies to let them know their RSV immunizations and therapies were going to see new scrutiny. Specifically, the companies involved are Merck, Sanofi and AstraZeneca, and their FDA-approved immunizations will have their safety data reviewed again, despite have gone through this exact process in recent years.

This continues as Health and Human Services Secretary Robert F Kennedy aims to review all vaccines and reduce greatly access to such immunizations.

The FDA’s drug division is “rigorously reviewing the available data, as it does for all products,” HHS spokesman Andrew Nixon said. “FDA routinely evaluates emerging safety information and will update product labeling if warranted by the totality of the evidence.”2

In a previous interview with Contagion, Helen Chu, MD, MPH, offers some insights on the previous burden of RSV prior to the immunizations, and the efficacy of 2 RSV products in preventing disease.

Specific Products Facing Review

The products being reviewed are Sanofi and AstraZeneca’s nirsevimab-alip (Beyfortus) and Merck’s clesrovimab-cfor (Enflonsia).

Nirsevimab was FDA approved in 2023, and clesrovimab was approved earlier this year during the current administration. Neither of the aforementioned products has shown any safety issues and having gone through the rigorous review process that is associated with getting federal approval.

no timeline was given for when the safety data will be reviewed or what the process will look like, including if there will be any public meetings or access to the information FDA officials are looking at.

We will continue to cover this evolving news. Check back for future coverage.

References
1. Levine D, Wingrove P. Exclusive: US FDA launches fresh safety scrutiny of approved RSV therapies for infants. Reuters. December 9, 2025. Accessed December 10, 2025
https://www.reuters.com/business/healthcare-pharmaceuticals/us-fda-launches-fresh-safety-scrutiny-approved-rsv-therapies-infants-2025-12-09/
2. Muller M, et al.FDA Taking Hard Look at Safety Data for RSV Shots for Babies. December 9, 2025. Accessed December 10, 2025.
https://www.bloomberg.com/news/articles/2025-12-09/fda-taking-hard-look-at-safety-data-for-rsv-shots-for-babies