COVID-19

Millions of people in dozens of countries have received the AstraZeneca Covid vaccine with few reports of ill effects, and its prior testing in tens of thousands of people found it to be safe.

But recently, blood clots and abnormal bleeding in a small number of vaccine recipients in European countries have cast doubt on its safety, although no causative link has been found between the patients’ conditions and the vaccine. The reports have prompted more than a dozen countries to either partly or fully suspend the vaccine’s use while the cases are investigated. Most of the nations said they were doing so as a precaution until leading health agencies could review the cases.