The FDA has required Guillain-Barré syndrome warnings to be added to prescribing information for RSV vaccines Abrysvo and Arexvy, citing postmarketing data suggesting an increased risk within 42 days of vaccination.
RT’s Three Key Takeaways:
- FDA Issues Guillain-Barré Warning for RSV Vaccines: The FDA has updated the prescribing information for Abrysvo (Pfizer) and Arexvy (GlaxoSmithKline) to include a warning about a potential increased risk of Guillain-Barré syndrome within 42 days of vaccination.
- Postmarketing Study Findings: An observational study using Medicare data estimated nine excess cases of Guillain-Barré syndrome per million doses of Abrysvo and seven per million doses of Arexvy among individuals aged 65 and older.
- Insufficient Evidence for Causality: While the study suggests an association between the vaccines and Guillain-Barré syndrome, the FDA notes that available evidence is insufficient to establish a causal relationship.
The US Food and Drug Administration (FDA) has required and approved a Guillain-Barré syndrome warning in the prescribing information for respiratory syncytial virus (RSV) vaccines Abrysvo, manufactured by Pfizer, and Arexvy, manufactured by GlaxoSmithKline Biologicals.
The prescribing information for each vaccine has been revised to include the following language in the Warnings and Precautions section:
- Abrysvo– The results of a postmarketing observational study suggest an increased risk of Guillain-Barré syndrome during the 42 days following vaccination with Abrysvo.
- Arexvy– The results of a postmarketing observational study suggest an increased risk of Guillain-Barré syndrome during the 42 days following vaccination with Arexvy.
Guillain-Barré syndrome is a rare disorder in which the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis.
Risk for Guillain-Barré Syndrome Following RSV Vaccination
FDA conducted a postmarketing observational study that assessed the risk of Guillain-Barré syndrome following vaccination with Abrysvo and Arexvy. Based on FDA’s evaluation of data from clinical trials, reports to the Vaccine Adverse Event Reporting System, and the postmarketing study, FDA has determined that the overall body of evidence suggests increased risks of Guillain-Barré syndrome with Abrysvo and Arexvy, but that available evidence is insufficient to establish a causal relationship.
The association between vaccination with Abrysvo and Arexvy and Guillain-Barré syndrome was evaluated among Medicare beneficiaries 65 years of age and older. Using Medicare claims data, between May 2023 through 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 Guillain-Barré syndrome among recipients of Abrysvo and Arexvy were identified through International Classification of Diseases codes. Guillain-Barré syndrome diagnoses in claims data were confirmed by medical record review when available.
The risks of Guillain-Barré syndrome following vaccination with Abrysvo and Arexvy were assessed in self-controlled case series analyses using risk windows of one to 42 days post-vaccination and control windows of 43 to 90 days post-vaccination. The analyses of all Guillain-Barré syndrome cases based on claims data suggest an increased risk of Guillain-Barré syndrome during the 42 days following vaccination, with an estimated nine excess cases of Guillain-Barré syndrome per million doses of Abrysvo, and an estimated seven excess cases of Guillain-Barré syndrome per million doses of Arexvy administered to individuals 65 years of age and older.
Background risks of Guillain-Barré syndrome in study populations influence excess Guillain-Barré syndrome case estimates and may differ between studies and analyses within a study, precluding direct comparisons of excess Guillain-Barré syndrome case estimates from other vaccine studies or populations.
While the results from the self-controlled case series analyses of this observational study suggest increased risks of Guillain-Barré syndrome with Abrysvo and Arexvy, available evidence is insufficient to establish a causal relationship.
