FDA Signals Fresh Safety Review of Infant RSV Treatments Amid Kennedy-Led Vaccine Policy Overhaul

U.S. health regulators have notified senior executives at Merck, Sanofi, and AstraZeneca that their FDA-approved infant RSV antibody treatments will undergo new safety scrutiny—another sign of shifting vaccine and pharmaceutical oversight under Health and Human Services Secretary Robert F. Kennedy Jr. The decision, confirmed by multiple sources and internal documents reviewed by Reuters, follows months of rising questions from Kennedy-appointed officials and independent analysts regarding safety signals and trial data.

The therapies under review—Sanofi and AstraZeneca’s Beyfortus, as well as Merck’s Enflonsia—are widely used preventive monoclonal antibodies designed to protect newborns from respiratory syncytial virus (RSV), a leading cause of hospitalization in infants. Unlike vaccines, these products provide ready-made antibodies rather than stimulating immune response, and have been integrated into the CDC’s recommended childhood immunization schedule.

The FDA’s new inquiry marks one of the most significant challenges yet to the products’ safety profile and comes at a politically charged moment for the administration’s broader realignment of vaccine policy in the United States.

A Regulatory Shift Under Kennedy

Since taking office, Kennedy has argued that the risks and long-term safety profiles of many pharmaceutical products have not been adequately studied. Medical organizations and several state officials have sharply disagreed, accusing him of undermining trusted vaccine programs. Yet Kennedy has continued to direct agencies to re-examine longstanding assumptions, data sources, and regulatory pathways.

According to HHS spokesperson Andrew Nixon, senior FDA adviser Dr. Tracy Beth Hoeg began raising internal safety questions about RSV products as early as June. Hoeg, who publicly criticized U.S. COVID-19 policies and has questioned elements of the childhood vaccine schedule, has since been elevated to acting director of the FDA’s Center for Drug Evaluation and Research (CDER)—a major position overseeing drug regulation.

Her inquiries prompted FDA officials to convene a call last week with the three pharmaceutical companies, signaling that further requests for data are coming. The call was brief and did not specify whether label changes, modified guidance, or restricted availability might follow.

“FDA routinely evaluates emerging safety information and will update product labeling if warranted by the totality of the evidence,” Nixon said, emphasizing that decisions remain “rooted in evidence-based science.”

What Sparked the Review?

The renewed scrutiny followed several converging developments:

• Internal FDA communications showing requests for a “second look” at Merck’s Enflonsia shortly after its approval.

• A widely shared blog post by Australian science journalist Maryanne Demasi, raising the possibility of seizure risk—claims not supported by existing safety studies.

• Internal discussions about mortality imbalances in clinical trials, flagged by Hoeg as worthy of re-examination despite not being statistically significant.

• Statements of regret from Dr. Robert Malone, a Kennedy-appointed vaccine advisory board member, who said he now questions his earlier recommendation for widespread Enflonsia use.

The review also arrives as Kennedy’s advisory committee made its most consequential policy shift to date: removing the long-standing recommendation that all U.S. newborns receive the hepatitis B vaccine at birth.

Taken together, these actions reveal a regulatory environment far more willing to question—and potentially unwind—elements of the existing childhood immunization framework.

Pharmaceutical Industry Pushback

Sanofi and Merck quickly defended the safety of their products.

• Sanofi stated that Beyfortus’ safety and efficacy profile is supported by “over 50 studies involving more than 400,000 infants.”

• Merck confirmed its meeting with FDA officials and welcomed “continued scientific dialogue,” expressing confidence in Enflonsia’s safety.

Multiple observational studies, including one from the CDC, have shown substantial benefits: up to a 43% reduction in RSV hospitalizations during the 2024–25 season.

Meanwhile, scientists such as Stanford infectious disease expert Dr. Jake Scott have pushed back against suggestions of seizure risk or data irregularities. Scott argues that combining newborns and older infants in safety analyses—as critics propose—would misattribute seizure events caused by other vaccines routinely administered to older babies.

“Rolling back RSV availability based on baseless concerns would do harm to American children,” he wrote, warning of a “dangerous precedent” in policymaking driven by flawed interpretation rather than established scientific processes.

What’s at Stake for Families?

RSV remains a major threat to young infants:

• 2–3 out of every 100 babies under six months are hospitalized with RSV each year.

• Severe cases can lead to respiratory failure, pneumonia, or death.

• Preventive antibody therapies offer protection during the most vulnerable window of life.

Whether the FDA inquiry ultimately results in label changes, dosage adjustments, or no action at all, the stakes are extraordinarily high—both for infant health outcomes and for parents navigating rapidly changing medical guidance.

What This Means for Public Health Policy

The unfolding RSV review is emerging as a test case for Kennedy’s broader reorientation of vaccine oversight. Several key dynamics are now in play:

• Regulators are revisiting assumptions that had previously been considered settled.

• Pharmaceutical companies are being asked to re-justify safety profiles for widely used pediatric products.

• Scientific advisory committees are divided, with some members reversing earlier positions and others warning of political interference.

• Parents and clinicians face new uncertainty as longstanding recommendations are reevaluated.

For Kennedy supporters, the inquiry represents long-overdue transparency in pharmaceutical regulation. For critics, it is a worrying sign that established public health protections may be weakened under pressure from anti-vaccine activism.

DailyClout Takeaway

The FDA’s move to re-examine infant RSV treatments, though still in early stages, is a revealing window into how U.S. health policy is shifting under Secretary Robert F. Kennedy Jr. The dispute raises fundamental questions about scientific evidence, regulatory independence, pharmaceutical accountability, and the future structure of childhood immunization.

Whether this moment leads to a more transparent, cautious, and data-rigorous regulatory system—or introduces new instability into pediatric care—will depend on how agencies communicate their findings, how industry responds, and how the public weighs evolving risk-benefit assessments in the months ahead.