As for GBS itself, this neurological ailment can be severe, attacking nerves and warranting hospitalisation for weeks or months. It can influence a variety of nerves from senses to movement, and even heart rhythm, with initial symptoms manifesting typically in the limbs.

Before the RSV vaccines were approved, the FDA flagged potential GBS risks with the vaccines. After approval, the CDC continued to monitor for GBS risk. FDA conducted a postmarket

Barré syndrome, although it said data don’t prove a causal link and affirmed the shots’ benefit outweighs their risks.

A post-marketing review by the FDA detected an increased risk of the autoimmune condition in patients inoculated with GSK’s Arexvy and Pfizer’s Abrysvo, prompting the regulator to require adjustments to the vaccines’ labels.

FDA updates safety labels for Pfizer's Abrysvo and GSK's Arexvy RSV vaccines, citing increased Guillain-Barré syndrome risk. Study estimates 7-9 excess GBS cases per million doses.

The FDA is adding a warning about Guillain-Barré syndrome to the respiratory syncytial virus vaccines manufactured by GSK and Pfizer based on data that suggest there may be a link between the shots and the rare disorder.

Barré for every million doses given.

GSK and Pfizer's respiratory syncytial virus (RSV) vaccines will carry warnings that they can increase the risk of developing a rare neurological disorder, the U.S. Food Drug Administration said on Tuesday.