The FDA has issued a warning regarding GlaxoSmithKline’s (GSK) shingles vaccines, Shingrix, and said it must include a label warning about the risk of Guillain-Barré syndrome (GBS), a rare disorder.

“In a postmarketing observational study, an increased risk of GBS was observed during the 42 days following vaccination with Shingrix,” the FDA said.

The FDA approved Shingrix in October 2017 as a two-dose regimen for preventing shingles in adults age 50 years and older.

GBS affects the body’s immune system and damages nerve cells, causing muscle weakness and in some cases paralysis.