U.S. FDA issues new warning for RSV vaccines Arexvy and Abrysvo

The U.S. Food and Drug Administration (FDA) is requiring a new warning in product information for the recombinant respiratory syncytial virus (RSV) vaccines Arexvy (GSK) and Abrysvo (Pfizer). The warning will alert healthcare providers about a possible increased risk of Guillain-Barré syndrome (GBS) within 42 days of administration of either vaccine.1 Both vaccines are approved in the United States (and Canada) to prevent lower respiratory tract disease caused by RSV in adults (consult Canadian product monographs2,3 for age ranges). Abrysvo is also indicated for use in pregnant women at 32–36 weeks’ gestation to prevent RSV-associated lower respiratory tract disease in their infants from birth through six months of age.1-3Based on information from the U.S. Centers for Disease Control, about 3000–6000 cases of GBS are reported annually in the United States. GBS is more common in men and in those older than 50 years of age. In many cases, GBS occurs following a viral or bacterial infection. Administration of some COVID-19 and seasonal influenza vaccines has also been associated with GBS.1The new U.S. warning is based on cases of GBS reported to the U.S. Vaccine Adverse Event Reporting System, as well as on data from clinical trials and a postmarketing observational study of Medicare data among persons ≥ 65 years of age. Scrutiny of this data revealed an increased risk of GBS during the 42-day period following vaccination. Compared to the risk 43–90 days post-vaccination, there were about nine additional cases of GBS per million doses with Abrysvo and seven additional cases per million doses with Arexvy. However, the FDA considers available evidence to be insufficient to establish a causal relationship for either vaccine.1 In the pivotal clinical trials that led to approval of Arexvy and Abrysvo, 12,467 patients received Arexvy and 17,215 received Abrysvo. GBS occurred in one patient nine days after vaccination with Arexvy and one case each of GBS and Miller Fisher syndrome (a variant of GBS) occurred seven and eight days, respectively, after vaccination with Abrysvo.1 These cases are currently mentioned in the Adverse Reactions section of the Canadian product monographs for Arexvy and Abrysvo.2,3GBS has not been reported to date with the mRNA RSV vaccine mResvia (Moderna). Therefore, product information for mResvia in the United States will not be updated to include a warning about an increased risk of GBS.1 There is no mention of any cases of GBS in the Canadian product monograph for MResvia.4Health Canada has not yet issued a specific warning regarding the increased risk of GBS with Arexvy and Abrysvo. However, the RSV vaccine chapter in the Canadian Immunization Guide notes that early safety data suggest a potential increased rate of inflammatory neurologic events, including GBS, after administration of these vaccines in adults 60 years of age or older.5 In addition, as stated above, GBS is mentioned as a possible adverse effect in the Canadian product monographs for Arexvy and Abrysvo. Canadian recommendations for the use of RSV vaccines (Arexvy and Abrysvo) in adults are available in the Canadian Immunization Guide,5 as well as in a statement from the National Advisory Committee on Immunization (NACI).6 NACI is currently reviewing the use of mResvia in adults, with plans to then issue updated recommendations on RSV vaccines and update the RSV vaccine chapter in the Canadian Immunization Guide.5 Despite the small increased risk of GBS associated with Arexvy and Abrysvo, the US FDA states that the benefits of vaccination with these vaccines outweigh the potential risk of GBS.1 References:Anon. In brief: new warning for the RSV vaccines Arexvy and Abrysvo. Med Lett Drugs Ther 2025;67(5095):1-2. (accessed January 16, 2025).GlaxoSmithKline Inc. Arexvy (respiratory syncytial virus vaccine, recombinant, AS01E adjuvanted) product monograph. Mississauga, ON; November 1, 2024. (accessed January 16, 2025).Pfizer Canada. Abrysvo (respiratory syncytial virus stabilized prefusion F subunit vaccine) product monograph. Kirkland, QC; December 21, 2023. (accessed January 16, 2025).Moderna Biopharma Canada Corporation. mResvia (respiratory syncytial virus mRNA vaccine) product monograph. Toronto, ON; November 6, 2024. (accessed January 16, 2025).Government of Canada. Respiratory syncytial virus (RSV) vaccines: Canadian Immunization Guide. For health professionals. August 2024. (accessed January 16, 2025).National Advisory Committee on Immunization. Statement on the prevention of respiratory syncytial virus disease in older adults. July 12, 2024. (accessed January 16, 2025).

U.S. FDA issues new warning for RSV vaccines Arexvy and Abrysvo

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