European Medicines Agency

"Its benefits continue to be far greater than its risks," said Dr. Sabine Straus of the agency's risk committee. It found no increase in the overall risk of blood clots with the vaccine.

Leaders from across the European Union's 27 member-states celebrated the start of vaccination efforts on Sunday. EU Commission President Ursula von der Leyen called it "a European success story."

Hours after the EU's drug agency signed off on the vaccine, the European Commission approved its use, clearing the way for inoculations to begin across Europe.