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.

Barré for every million doses given.

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

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.

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.