FDA Requires RSV Vaccine Labels to Include Guillain-Barré Syndrome Risk

On Jan. 7, 2025, the U.S. Food and Drug Administration (FDA) mandated and approved changes to the safety labeling for the Prescribing Information of two Respiratory Syncytial Virus (RSV) vaccines: Abrysvo (manufactured by Pfizer)¹ and Arexvy (manufactured by GlaxoSmithKline Biologicals).²

This label change update is being required to inform both the public and health care providers about the Guillain-Barré syndrome (GBS) risk.³ The Prescribing Information for each vaccine has been revised to include the following statements in the Warnings and Precautions section:

• “A post-marketing observational study suggests an increased risk of Guillain-Barré syndrome (GBS) within 42 days following vaccination with Abrysvo.”
• “A post-marketing observational study suggests an increased risk of Guillain-Barré syndrome within 42 days following vaccination with Arexvy.”⁴

GBS is a condition where the immune system attacks the body’s nerves, potentially causing weakness, numbness, or paralysis. The condition typically starts with weakness and tingling in the hands and feet, which can rapidly spread and may progress to paralysis. In its severe form, GBS is a medical emergency, and most individuals with the condition require hospital treatment.⁵

Age Use Recommendation for RSV Vaccine Also Changed

The FDA approved both Abrysvo and Arexvy for use in adults aged 60 and older in May 2023. Both vaccines experienced high sales during their first year on the market. However, seven months ago, the sales potential for both vaccines dropped significantly after the U.S. Centers for Disease Control and Prevention (CDC) revised its recommendations use only for adults aged 75 years and older, or those 60 and older with a high risk of severe disease due to underlying medical conditions.⁶

The FDA carried out a post-marketing observational study to evaluate the risk of GBS after receiving Abrysvo and Arexvy. Based on its review of clinical trial data, reports from the Vaccine Adverse Event Reporting System (VAERS), and the post-marketing study, the FDA concluded that the evidence indicates an increased risk of GBS with both vaccines.⁷

Medicare Study Links Increased GBS Risk to RSV Vaccines in Older Adults

The link between vaccination with Abrysvo and Arexvy and the risk of GBS was assessed among Medicare beneficiaries aged 65 and older. Using Medicare claims data from May 2023 to July 2024, researchers identified vaccinations with Abrysvo and Arexvy through Current Procedural Terminology (CPT) codes, Healthcare Common Procedure Coding System (HCPCS) codes, and National Drug Codes. Potential cases of hospitalized GBS among vaccine recipients were identified using International Classification of Diseases (ICD) codes, with diagnoses confirmed by medical record review when available.⁸

The study assessed the risk of GBS following vaccination through self-controlled case series analyses, comparing risk periods of 1 to 42 days after vaccination to control periods of 43 to 90 days.

The findings from these analyses indicated an increased risk of GBS in the 42 days following vaccination. Specifically, there were an estimated nine excess cases of GBS per million doses of Abrysvo and seven excess cases per million doses of Arexvy in individuals aged 65 and older. However, the background risk of GBS in the study population can influence these estimates, meaning that comparisons of excess GBS cases between different vaccine studies or populations may not be directly applicable.⁹

In response to the FDA’s safety label requirement, a spokesperson for GSK minimized the importance of the GBS risk finding related to its RSV vaccine, stating,“While the results of this observational study suggest an increased risk of GBS with Arexvy, available evidence is insufficient to establish a causal relationship.”¹⁰

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