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FDA Requires Warning for Guillain-Barré Syndrome in Prescribing Information for RSV Vaccines
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Key Takeaways
- The FDA requires a GBS warning for RSV vaccines Abrysvo and Arexvy due to increased risk within 42 days post-vaccination.
- Clinical trials and postmarketing data show rare GBS cases, with Arexvy reporting more adverse events than Abrysvo.
Despite these concerns, experts have emphasized that the benefits of RSV vaccination outweigh potential risks for older adults, who are at heightened risk of severe RSV-related illness.
The FDA is now requiring a safety labeling change in the prescribing information for the respiratory syncytial virus (RSV) vaccines Abrysvo (Pfizer) and Arexvy (GSK), notifying recipients of an increased risk of Guillain-Barré syndrome (GBS) during the 42 days following vaccination.1
RSV vaccine vial and syringe | Image credit: kitsawet | stock.adobe.com
GBS is a rare disorder in which the body’s immune system damages nerve cells, resulting in muscle weakness and, in severe cases, paralysis.1 GBS was identified as a potential concern in clinical trials with both Arexvy and Abrysvo, both of which were approved in May 2023 for the prevention of RSV-associated lower respiratory tract disease in adults 60 years or older. After their approval, data from V-safe and the Vaccine Adverse Event Reporting System (VAERS) showed that rates of GBS after vaccination were higher than estimated at 4.4 and 1.8 reports per million doses of Abrysvo and Arexvy, respectively.2
Despite these concerns, experts have emphasized that the benefits of RSV vaccination outweigh potential risks for older adults, who are at heightened risk of severe RSV-related illness.2
According to research findings presented at the American Society of Health-System Pharmacists Midyear 2024 Clinical Meeting, researchers found that GBS remains rare among older adults after RSV vaccination, although they noted that Arexvy reported more than twice as many serious adverse events than Abrysvo. Furthermore, more adverse events were reported in individuals aged 60 to 74, compared with those 75 years or older. There was also a higher incidence of serious adverse events in women than in men.2
The FDA conducted its own postmarketing observational study to evaluate the risk of GBS following RSV vaccination in older adults. Their decision to include a safety warning is based on data from the clinical trials, VAERS reports, and the postmarketing study.1
“[The] FDA has determined that the overall body of evidence suggests increased risk of GBS with Abrysvo and Arexvy, but that available evidence is insuffient to establish a causal relationship,” FDA officials wrote in the news release.1
Using Medicare claims data between May 2023 and July 2024, vaccinations with Abrysvo and Arexvy were identified through Current Procedural Terminology/Healthcare Common Procedure Coding System codes and National Drug Codes, and potential cases of hospitalized GBS among vaccine recipients were identified via International Classification of Diseases codes. The risks of GBS following vaccination were assessed in self-controlled case series analyses using risk windows of 1 to 42 days post-vaccination and control windows of 43 to 90 days post-vaccination.1
According to the study results, the findings suggest an increased risk of GBS during the 42 days following vaccination, with an estimated 9 excess cases of GBS per million doses of Abrysvo and an estimated 7 excess cases of GBS per million doses of Arexvy in individuals 65 years and older. The news release noted that background risks of GBS in the study population can influence excess GBS case estimates and may differ between studies and analyses within a study.1
In clinical trials supporting the original FDA approval of Abrysvo, approximately 22,000 individuals received the vaccine and 22,000 received placebo. Among study participants 60 years of age and older, 1 participant developed GBS 7 days after vaccination and another developed Miller-Fisher syndrome (a variant of GBS) 8 days after vaccination. The initial FDA approval included a requirement for Pfizer to conduct a study evaluating the risk of GBS among approximately 1.5 million older adults vaccinated with Abrysvo.1
Similarly, in the clinical trials supporting the initial approval of Arexvy, approximately 16,000 received the vaccine and 13,000 received placebo. In the Arexvy group, 1 participant developed GBS 9 days after vaccination. The FDA has also required GSK to conduct a study evaluating the risk of GBS among 1.9 million adults 50 years of age and older vaccinated with Arexvy.1
“FDA has further determined that the benefits of vaccination with Abrysvo and Arexvy continue to outweigh their risks,” the news release said. “Continuous monitoring and assessment of the safety of all vaccines remain an FDA priority and we are committed to informing the public when we learn new information about these vaccines.”1
Pharmacists play a vital role in patient safety, particularly in the context of vaccination. By diligently monitoring patients for adverse events and educating them about symptoms, pharmacists contribute to the overall success of vaccination programs. Pharmacists’ expertise in vaccine safety, coupled with their accessibility to patients, makes them invaluable partners in identifying and mitigating potential risks associated with vaccines. Continued education and collaboration between pharmacists, physicians, and public health officials is crucial to ensure the safe and effective use of vaccines.
