The European Medicines Agency (EMA) said on Tuesday it was analysing data on rare cases of a nerve disorder reported among recipients of Johnson & Johnson's Covid-19 vaccine, after the United States added a warning label to the shot.
The "EMA's safety committee (PRAC) is analysing data provided by (J&J) ... on cases of Guillain-Barre syndrome (GBS) reported following vaccination," the European medicines regulator said in a statement to Reuters. "PRAC has requested (Johnson & Johnson) to provide further detailed data."
The EMA scrutiny comes after the US Food and Drug Administration (FDA) on Monday added a warning for GBS to the fact sheet for J&J's shot, and after the EMA four days ago included a warning for AstraZeneca's Covid-19 shot for people to be on alert for potential side effects.
Around 12.8 million people have received J&J's one-dose vaccine in the United States, while J&J has distributed 18.6 million doses to European Union countries, according to the European Centre for Disease Prevention and Control.
In its decision to add a warning label, the FDA said 100 preliminary reports of GBS included 95 serious cases that required hospitalization and one reported death.
The EMA said its review was part of regular summary safety reports for J&J's shot, and didn't give any details about potential GBS cases in Europe.
Britain's MHRA drug regulator said separately on Tuesday it was also reviewing cases of GBS in vaccinated people, but said that so far, "our review has not established that these vaccines increase the risk of GBS". AstraZeneca's vaccine is widely used in Britain, though J&J's shot has yet to be deployed there.
GBS is a rare neurological condition in which the body's immune system attacks nerve fibres' protective coating. Most cases follow a bacterial or viral infection. Most people fully recover from GBS.
AstraZeneca's and J&J's shots, which rely on a viral vector to deliver genetic information to kick off the body's immune response to Covid-19, already include warnings about very rare, but potentially deadly, blood clotting.