The U.S. Food and Drug Administration (FDA) has announced that the prescribing information for two newly approved RSV vaccines, Abrysvo and Arexvy, will now include warnings regarding an increased risk of Guillain-Barré Syndrome (GBS) within 42 days of vaccination. Although the FDA has not found sufficient evidence to conclusively link the vaccines to GBS, ongoing surveillance and monitoring are deemed necessary. Despite these concerns, the benefits of these vaccines continue to surpass the potential risks, with both vaccines proving effective in preventing lower respiratory tract disease (LRTD) caused by RSV.
Approved earlier this year, Abrysvo received FDA approval on May 31, 2023, for adults aged 60 and above, while Arexvy was approved on May 3, 2023, for the same age group. Since then, Abrysvo has expanded its approval to include adults aged 18-59, and Arexvy now covers those aged 50-59. The decision to include a warning is based on clinical trial findings where isolated cases of GBS were reported shortly after vaccination.
During clinical trials, one case of GBS was documented nine days post-Abrysvo vaccination. Similarly, Arexvy's trials recorded a case of GBS and a variant known as Miller-Fisher syndrome occurring seven and eight days after vaccination, respectively. A postmarketing study using Medicare claims data from May 2023 through July 2024 supported these findings, though no direct causal relationship was established.
“There is still uncertainty regarding the amount of increased GBS risk associated with these vaccines, and whether any specific factors may increase the risk,” said Shirin A. Mazumder, MD.
In contrast, no cases of GBS have been reported in association with Moderna's mResvia RSV vaccine, licensed in 2024. This underscores the importance of continued research to identify any additional risk factors that could contribute to the development of GBS following RSV vaccination.
Despite these cautionary measures, the Centers for Disease Control and Prevention (CDC) continues to advocate for the RSV vaccination, particularly for adults over the age of 75 and those aged 60-74 who are at increased risk for severe disease. Current data robustly supports the safety and efficacy of these vaccines in preventing serious complications from RSV.
“vaccine safety monitoring programs are critical to gain more information to make the most appropriate preventative health recommendations,” emphasized Shirin A. Mazumder, MD.
The warnings serve as a precaution while researchers continue to explore any possible correlations between the vaccines and GBS. Dr. Mazumder notes that further research is essential to better understand any additional factors that might elevate the risk of GBS in vaccinated individuals.
“Also, further research is needed to determine any additional factors that may increase the risk of GBS in those receiving the RSV vaccine,” stated Dr. Mazumder.
Healthcare professionals are encouraged to discuss potential risks with patients who are considering vaccination. This dialogue ensures informed decision-making while promoting confidence in public health measures.
“but it is a discussion that should be held with the patient,” added Dr. Mazumder.
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