The US Food & Drug Administration (FDA) has issued a safety alert linking possible Guillain-Barré syndrome (GBS) with two respiratory syncytial virus (RSV) vaccines – one from Pfizer (Abrysvo) and the other from GSK (Arexvy).
The prescribing information for each jab has been revised to say that a post-marketing observational study suggested an increased risk of GBS in the 42 days after vaccination.
MedicalBrief notes that RSV vaccines are currently not available in South Africa, but according to a research paper in the South African Medical Journal by Z Dangor, et al in November last year, 'two new RSV prevention strategies have emerged: nirsevimab, a long-acting monoclonal antibody, and a maternal RSV vaccine. Both strategies have shown high efficacy in reducing RSV-LRTI hospitalisation in infants and are being considered for licensure in SA'.
GBS is a rare, acquired demyelinating polyneuropathy that causes muscle weakness, often beginning in the lower extremities and ascending over time with loss of reflexes, reports Medpage Today. It sometimes leads to paralysis.
Before their approval, the FDA flagged potential GBS risks with the two vaccines. After they were given the green light, they have continued to be monitored for GBS risk.
The FDA also conducted a post-marketing observational study, and based on the agency’s review of clinical trial data, reports to the Vaccine Adverse Event Reporting System (VAERS), and the post-marketing study, determined that the overall body of evidence suggested increased risks of GBS with both vaccines, but that available evidence was not enough to establish a causal relationship.
The post-marketing study was a self-controlled case series analysis using risk windows of one to 42 days post-vaccination and control windows of 43 to 90 days post-vaccination.
The claims data suggested an increased risk of GBS during the 42 days after vaccination, with an estimated nine excess cases of GBS per million doses of Abrysvo, and an estimated seven excess cases of GBS per million doses of Arexvy administered to people 65 and older.
Abrysvo and Arexvy were initially approved in May 2023 to prevent lower respiratory tract disease (LRTD) caused by RSV in people 60 and older. Since then, Abrysvo has been approved to prevent LRTD caused by RSV in people aged 18 to 59 who are at increased risk for LRTD caused by RSV, and to immunise pregnant women to prevent LRTD caused by RSV in infants.
Arexvy also has been subsequently indicated for people 50 to 59 who are at increased risk for LRTD caused by RSV.
The FDA said the benefits of vaccination with the two RSV vaccines continue to outweigh their risks.
Medpage Today article – DA Adds Guillain-Barre Syndrome Warning to Two RSV Vaccines (Open access)
See more from MedicalBrief archives:
CDC updates age criteria for RSV jabs
RSV jab may boost Guillain-Barré risk, US experts warn