In a significant development for vaccine safety, the U.S. Food and Drug Administration (FDA) has issued a comprehensive warning regarding the RSV vaccines produced by Pfizer (Abrysvo) and GlaxoSmithKline (Arexvy), highlighting potential neurological risks that demand immediate attention from healthcare professionals and the public.

The FDA's extensive post-market observational study has revealed a concerning pattern of increased risk for Guillain-Barré Syndrome (GBS), a rare but serious neurological disorder characterized by the immune system's attack on nerve cells, potentially leading to muscle weakness and, in severe cases, paralysis. The research meticulously analyzed clinical trial data, vaccine adverse event reporting systems, and post-market surveillance to reach its conclusions.

Quantitative findings from the study are particularly noteworthy. For Abrysvo, researchers estimated an increase of approximately 9 additional GBS cases per million vaccine doses, while Arexvy showed a slightly lower but still significant increase of 7 additional cases per million doses. These statistics were derived from a comprehensive examination of Medicare claims data collected between May 2023 and July 2024, focusing on individuals aged 65 and older.

Both vaccines, initially approved in May 2023, were developed to prevent lower respiratory tract diseases (LRTD) caused by respiratory syncytial virus (RSV) in older adults and specific at-risk populations. Abrysvo's approval expanded to include prevention for adults 18-59 with increased RSV risk and pregnant women seeking to protect their infants. Arexvy similarly targeted adults 60 and older, with a subsequent approval for the 50-59 age group.

Clinical trials preceding the vaccines' approvals had already documented isolated GBS cases. In Abrysvo's trials involving approximately 22,000 vaccine recipients, one participant developed GBS seven days post-vaccination, while another experienced Miller Fisher syndrome, a GBS variant. Arexvy's clinical trials, which included around 16,000 participants, similarly reported one GBS case nine days after vaccination.

Despite these findings, the FDA emphasizes that the benefits of these vaccines continue to outweigh the potential risks. The agency has mandated safety label updates for both Abrysvo and Arexvy, requiring healthcare providers to inform patients about the potential GBS risk. Furthermore, the FDA remains committed to continuous vaccine safety monitoring and pledges to promptly communicate any new developments to the public.

This warning serves as a critical reminder of the ongoing importance of post-market surveillance in vaccine development and the pharmaceutical industry's responsibility to transparently communicate potential risks to healthcare consumers.

Source ▏‍FDA‍