A British trial of the AstraZeneca COVID-19 vaccine in children is on hold, amid an investigation to a possible link with blood clots.

The developers of the vaccine say there are no safety concerns associated with the trial, but they’re awaiting information from the UK regulator on its review of rare cases of blood clotting in adults.

Europe’s medical watchdog says it’s yet to reach a conclusion on whether there’s a link between the vaccine and blood clots.

The head of vaccine strategy for the European Medicines Agency (EMA), Marco Cavaleri, has been quoted in Italian media as saying there was a “clear” connection.

Asked about the comments, the EMA press office says no conclusion has been reached and a review is ongoing.