FDA Requires Guillain-Barré Syndrome Warning on 2 RSV Vaccines
The federal agency approved safety labeling changes to the prescribing information for Abrysvo (Pfizer) and Arexvy (GSK) RSV vaccines for seniors after data from clinical trials, reports to the Vaccine Adverse Event Reporting System (VAERS), and a postmarketing study.
Image credit: FDA
The FDA announced it has required safety labeling changes to the prescribing information for both the RSV vaccines to include a warning for the rare neurological disorder, Guillain-Barré Syndrome (GBS).1
The agency said it conducted a postmarketing observational study that assessed the risk of GBS following vaccination with Abrysvo and Arexvy. Based on FDA’s evaluation of data from clinical trials, reports to the Vaccine Adverse Event Reporting System (VAERS), and the postmarketing study, FDA determined that the overall body of evidence suggests increased risks of GBS with Abrysvo and Arexvy, but that available evidence is insufficient to establish a causal relationship.1
The association between vaccination with the 2 RSV vaccines and GBS 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 (CPT)/Healthcare Common Procedure Coding System (HCPCS) codes and National Drug Codes, and potential cases of hospitalized GBS among recipients of Abrysvo and Arexvy were identified through International Classification of Diseases (ICD) codes. GBS diagnoses in claims data were confirmed by medical record review when available.1
The risks of GBS following vaccination with Abrysvo and Arexvy 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. The analyses of all GBS cases based on claims data 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 administered to individuals 65 years of age and older. Background risks of GBS in study populations influence excess GBS case estimates and may differ between studies and analyses within a study, precluding direct comparisons of excess GBS case estimates from other vaccine studies or populations.1
While the results from the self-controlled case series analyses of this observational study suggest increased risks of GBS with Abrysvo and Arexvy, available evidence is insufficient to establish a causal relationship.1
GBS is a condition where an individual’s immune system mistakenly attacks part of his or her peripheral nervous system.2
Read more: RSV Vaccine for Immunocompromised Seniors Shows Limited Seroconversion
According to the NIH, GBS begins suddenly and can increase in intensity over a period of hours, days, or weeks until certain muscles cannot be used at all. Some cases of GBS are very mild and only marked by brief weakness. Others cause nearly devastating paralysis, leaving the person unable to breathe on their own. In these cases, the disorder is life-threatening—potentially interfering with breathing, blood pressure, or heart rate.2
There is no cure for GBS, but some treatment can reduce severity of the disorder and shorten recovery time. Fortunately, most people eventually recover from even the most severe cases of GBS. After recovery, people may continue to have some weakness.2
