FDA adds warning of rare neurological reaction to J&J Covid-19 vaccine

US regulators on Monday added a new warning to Johnson & Johnson's COVID-19 vaccine about links to a rare and potentially dangerous neurological reaction, but said it's not entirely clear the shot caused the problem.

The Food and Drug Administration announced the new warning, flagging reports of Guillain-Barre syndrome, an immune system disorder that can causes muscle weakness and occasionally paralysis. Health officials described the side effect as a small possible risk" for those getting the shot.

The action comes after the FDA and the Centers for Disease Control and Prevention reviewed reports of about 100 people developing the syndrome after receiving the one-dose vaccine. Almost all of them required hospitalization and one person died, the FDA said.

Guillain-Barre syndrome occurs when the body's immune system mistakenly attacks some of its nerve cells, causing muscle weakness and sometimes paralysis that typically is temporary. An estimated 3,000 to 6,000 people develop the ..