AstraZeneca’s COVID-19 vaccine is “safe and effective” and should continue to be used, the European Medicines Agency announced today after a review of concerns about blood clotting.

But the agency said it could not rule out a link with two rare blood-clotting conditions seen in 25 people who were given the vaccine. It added that warnings should be included with information about the vaccine provided to doctors and patients. Nine of these people have died.