Are RSV shots next in line for restrictions in the US?

After pushing for restrictions on vaccines for COVID-19 and hepatitis B, the Trump administration seems to be turning its attention to recently approved shots that protect infants against respiratory syncytial virus (RSV).

According to a Reuters report, the FDA has launched an investigation into the safety of antibody-based preventative medicines – Sanofi/AstraZeneca's Beyfortus (nirsevimab) and MSD's Enflonsia (clesrovimab) – that are currently recommended to prevent infants from RSV infections.

If confirmed, the safety review could herald the imposition of restrictions on the use of the antibodies by HHS, which has been changing long-established US policies on paediatric vaccinations under Secretary Robert F Kennedy Jr, a longstanding promoter of anti-vaccine rhetoric.

Under his watch, there has been a concerted effort to claim that even well-established interventions like hepatitis B vaccines have not been properly tested for safety, amid accusations that political appointees and advisors to HHS agencies are cherry-picking data that suggest they are unsafe.

Those concerns prompted a dozen former FDA Commissioners to publish an article in the New England Journal of Medicine last week, saying that the change to childhood immunisation policies "breaks sharply with the norms that have anchored the FDA's globally respected scientific integrity."

According to the news agency, HHS officials started making enquiries into RSV antibodies during the summer, and there have already been unsubstantiated suggestions that they may be linked to an increased risk of seizures.

The risk that access to the antibodies may become difficult has caused dismay among public health and paediatric experts, given that RSV causes an average of around 58,000 hospitalisations in children aged five and under a year in the US, with somewhere between 100 and 500 deaths, according to CDC information published last year.

Earlier this year, another CDC report suggested that infant hospitalisations due to the virus had fallen by up to 43% in 2024 compared to previous years, which it attributed to the widespread rollout of preventative RSV shots.

The virus is the second-largest killer of children worldwide after malaria, with deaths disproportionately seen in low-income countries.

Restrictions could slam the brakes on the rollout of two products that have been predicted to become major earners for their developers, given that Beyfortus achieved blockbuster status in 2024, in its first full year on the market after getting FDA-approved in 2023, with sales of $1.8 billion that were driven by the US. MSD has not yet reported any sales figures for Enflonsia, which was approved by the FDA in June.

Sanofi and MSD have said they stand by the data behind their antibodies and are happy to enter into a dialogue with the FDA on their safety and efficacy.