The US Food and Drug Administration (FDA) has ordered updates to the safety labeling of respiratory syncytial virus (RSV) vaccines.Abrysvo from Pfizer Inc (NYSE:PFE) et d’Arexvy’s (NYSE:GSK) to include warnings about an increased risk of Guillain-Barré syndrome (GBS).
New warnings in the prescriptive information highlight a potential increased risk of Guillain-Barré syndrome (GBS), a rare neurological disorder, within 42 days of vaccination, based on the results of a post-vaccination observational study. -marketing.
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GBS is a condition in which the immune system attacks nerve cells; it can lead to muscle weakness and, in severe cases, paralysis.
According to the FDA, although the evidence suggests an increased risk, it is not enough to confirm a definitive causal link between vaccines and the disorder.
This determination is based on data from clinical trials, adverse event reports, and an observational study of Medicare beneficiaries aged 65 and older.
The study, conducted between May 2023 and July 2024, used Medicare claims to identify hospitalized GBS cases in people vaccinated with Abrysvo or Arexvy.
Using a self-controlled case series analysis, researchers compared risk windows of 1 to 42 days after vaccination (risk window) to control windows of 43 to 90 days. The results estimate nine additional cases of GBS per million doses of Abrysvo and seven cases per million doses of Arexvy administered to individuals aged 65 and older.
These risks reflect additional cases relative to background rates of GBS in the study population. However, variations in background risks and analytical methods make direct comparisons with other studies difficult. The FDA emphasized that although increased risks have been observed, additional research is needed to fully understand the link between vaccines and GBS.
U.S. sales of respiratory syncytial virus vaccines declined after regulators narrowed the age group eligible for the shots and determined they would be a one-time vaccination for now.
For Pfizer and GSK, RSV vaccines are crucial as they seek to create new revenue streams before facing generic competition for their best-selling drugs.
Price movement: At last trading Wednesday, GSK’s stock was down 1.55% at $33.56, and PFE’s stock was down 0.18% at $27.08 during pre-market trading.
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