RFK, Jr., Questions Safety of Approved RSV Shots for Babies

U.S. health officials are probing the safety of two infant RSV therapies—Sanofi/AstraZeneca’s Beyfortus and Merck’s Enflonsia—after FDA inquiries began over the summer amid unproven claims from vaccine skeptics about seizure risk; both products were approved for infants (Beyfortus in 2023, Enflonsia in June 2025) and underwent extensive clinical testing. The investigation, taking place under HHS Secretary Robert F. Kennedy Jr. and following a recent advisor panel decision to rescind a universal newborn hepatitis B recommendation, comes as the CDC continues to recommend maternal RSV vaccination between 32–36 weeks during the September–January period. The scrutiny risks affecting public confidence, uptake and future policy guidance on RSV prevention for infants.

Analysis

U.S. health officials are probing the safety of two infant RSV therapies—Sanofi/AstraZeneca’s Beyfortus and Merck’s Enflonsia—after FDA inquiries began over the summer; Beyfortus was approved in 2023 and Enflonsia in June 2025. Vaccine skeptics have alleged, without evidence, an increased seizure risk in infants; the agencies are investigating those claims while noting that both products were extensively tested in clinical trials prior to approval.

The scrutiny is unfolding under HHS Secretary Robert F. Kennedy Jr., whose handpicked vaccine advisors recently voted to rescind a universal newborn hepatitis B recommendation, a development that increases political and regulatory risk around vaccine policy. The CDC nonetheless continues to recommend that pregnant people receive an RSV vaccine between 32 and 36 weeks during the September–January window, preserving a public-health pathway for infant protection pending the probe.

Market signals in the article point to moderately negative sentiment (sentiment_score -0.4, market_impact_score 0.33) and could translate into near-term uptake headwinds, reputational damage and share volatility for SNY, AZN and MRK if the investigation yields safety concerns. Key immediate drivers will be FDA statements, reported adverse-event data and any changes to public-health recommendations rather than the original trial efficacy findings.

Key Decisions for Investors

• Monitor FDA investigation updates and reported adverse-event data closely, because any substantiated safety signal would materially affect uptake and valuations for SNY, AZN and MRK
• Expect near-term sentiment-driven volatility and consider trimming new long exposure or staging purchases until regulatory clarity and federal guidance are available
• Use options or other hedges to protect existing positions rather than exiting outright, since the products were extensively trialed and a null finding could create a recovery opportunity
• Watch CDC guidance, HHS communications and September–January uptake metrics as leading indicators of commercial impact and policy risk