THE EUROPEAN MEDICINES Agency (EMA) is seeking further information from Johnson & Johnson after US regulators added a warning to the firm’s Janssen Covid-19 vaccine over links to a rare neurological reaction.

The EMA’s safety committee (PRAC) is analysing data provided by Johnson & Johnson on cases of Guillain-Barre syndrome reported following vaccination with the one-dose shot.

“PRAC has requested the marketing authorisation holder (Johnson & Johnson) to provide further detailed data,” the regulator said in a statement to The Journal.

EMA will continue its review of the cases and will communicate further when new information becomes available.

The US Food and Drug Administration (FDA) 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”.

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 hospital admission 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 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 shot. Most cases were reported in men — many aged 50 and older — and usually about two weeks after vaccination.

J&J said it has been discussing the reports with the FDA and other health regulators around the world.

The CDC said it will ask its panel of outside vaccine experts to review the issue at an upcoming meeting.

The new warning will be included in pamphlets given to people getting the J&J vaccine. They should seek medical attention if they experience any symptoms, which include tingling sensations, trouble walking and double vision, the FDA said.

Vaccines historically provide broad protection with little risk but come with occasional side effects just like other drugs and medical therapies.

The four Covid-19 vaccines used in Ireland, including the Janssen jab, were each tested in tens of thousands of people, but even such huge studies cannot rule out extremely rare side effects.

The most recent stats from the HSE show that, as of yesterday, a total of 72,092 doses of the Janssen vaccine have been administered in Ireland. This represents 1.5% of the total number of vaccines delivered so far.

The jab recently became available to 18-35 year-olds through pharmacies, subject to supply.

Guillain-Barre can be triggered by a number of infections, including flu, cytomegalovirus and Zika virus, but there have been rare cases in which people develop the disorder days or weeks after receiving certain vaccines.

With reporting from Press Association