US regulators have added a new warning to Johnson & Johnson's (Janssen) 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 cause 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 Centres 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 hospitalisation 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 3000 to 6000 people develop the syndrome each year, according to the CDC.
The number of cases reported in connection with J&J's vaccine represents a tiny fraction of the nearly 13 million Americans who have received the one-dose shot. Most cases were reported in men — many 50 years old and up — and usually about two weeks after vaccination.
