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.

The FDA will require GSK and Pfizer to include on the label of their respiratory syncytial virus (RSV) vaccines a warning about the risk of developing Guillain-Barré syndrome (GBS), a rare neurological condition that can cause paralysis.

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

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.

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.

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.

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.

GSK Plc and Pfizer Inc.’s vaccines for a common respiratory virus must carry warnings that they may be tied to an increased risk of a rare neurological side effect that can lead to paralysis, the US Food and Drug Administration said.