The University of Oxford says it is suspending a trial on children and teenagers of the COVID-19 vaccine it developed with British drug maker AstraZeneca.
The move came after reports from European countries of blood clots among adults who received the vaccine.
The university announced on Tuesday the suspension of the trial, which it began in February on people aged 17 or younger in Britain.
It stressed that there were no safety concerns in the pediatric trial. But it said it would await more guidance from the British drugs watchdog, the Medicines and Healthcare products Regulatory Agency, before proceeding further with it.
Germany and France had previously suspended the use of the vaccine due to the blood-clotting issue.
But the European Medicines Agency, which is the European Union's drug regulatory agency, said in a review in March that the vaccine is safe and effective. It added that the vaccine's benefits outweigh its possible risks.
The EMA is expected to release updates about further findings soon.