Following the FDA’s acceptance for review of a Biologics License Application for Pfizer’s respiratory syncytial virus (RSV) vaccine candidate, the agency has asked for further studies into the connection between the vaccine and cases of Guillain-Barré syndrome (GBS). Documents released in February 2023 indicate that if the vaccine is approved, “post-marketing surveillance” will be warranted.  

GBS and the vaccine 

Guillain-Barré syndrome (GBS) sometimes occurs when the immune system affects the peripheral nervous system, often after an infection. It is most commonly observed in the hands or feet, before spreading to other parts of the body, with symptoms such as numbness, muscle weakness, or pain.  

The FDA reports than one case of GBS was identified 7 days after vaccination, with a case of Miller Fisher syndrome, “considered a variant of GBS”, identified 8 days after vaccination. Thus, a total of 2 cases among 19,942 vaccinated participants were recorded. The FDA puts this into the context of a background rate of 1.5-3 cases per 100,000 people each year among US adults. Consequently, it is requesting that GBS and other “immune-mediated demyelinating conditions” are included in the Pharmacovigilance Plan (PVP).  

Furthermore, the FDA requests that Pfizer proposes a post-marketing safety study to assess the risk of GBS and other conditions among vaccine recipients post-licensure. Pfizer stated that it will do this.  

The race continues 

Despite this hurdle, Pfizer continues to keep pace in the race for an RSV vaccine with competitors such as GSK and Moderna also developing candidates. CNN reports that GSK also reported a ‘potential case” of GBS among vaccine recipients but found “insufficient evidence” for confirmation of a diagnosis.  

Data for both GSK and Pfizer candidates is under consideration by the CDC, with “post licensure surveillance” being described as “critical” by the Advisory Committee on Immunisation Practices.  

For more updates on RSV from key players in the vaccine industry, join us at the World Vaccine Congress in Washington this April.