There is a causal link between the coronavirus vaccine developed by AstraZeneca and very rare cases of blood clots, although it remains unclear what the connection is and the possible causes are likewise still unknown, a senior European Medicines Agency (EMA) expert told an Italian on Tuesday. "It is clear that an association exists" between the vaccine and the dozens of reported blood clots, said Marco Cavaleri, head of the EMA's health threats and vaccines strategy.

"Such cases are extremely rare, and the benefits (of the vaccine) still largely outweigh the risks," he stressed. "Yet, it is becoming increasingly hard to say there is no cause-effect relationship between the vaccination with AstraZeneca and very rare cases of unusual blood clots associated with a low number of platelets," he said.