No specific risk factors including age have been identified for blood clots with the AstraZeneca coronavirus vaccine, which could stem from an immune response, the EU's drug regulator said Wednesday. "Specific risk factors such as age, gender or medical history have not been able to be confirmed, as the rare events are seen in all ages," European Medicines Agency chief Emer Cooke told a news conference. "A plausible explanation for these rare side effects is an immune response to the vaccine." dk/dl