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.
The AstraZeneca vaccine has not been authorized for use yet in the United States, although a review of its U.S. trial is expected soon.
What types of problems caused the countries to take precautionary steps?
The cascade of decisions to pause the use of AstraZeneca’s vaccine, mainly by European countries, followed reports of four serious cases in Norway, which were described among health workers under age 50 who received the vaccine. Most developed clots or bleeding abnormalities and had low platelet counts, health authorities there said. Two of them have died from brain hemorrhages, and the other two are hospitalized. The death of a 60-year-old woman in Denmark and of a 57-year-old man in Italy also fueled quick decisions, although none of the deaths have been fully investigated to determine whether there is any link to the shots they received.
300,000 to 600,000 people a year in the United States develop blood clots in their lungs or in veins in the legs or other parts of the body, according to the Centers for Disease Control and Prevention.
9.7 million doses of the vaccine had been given out through last month. Britain’s data found that at least some clotting conditions, while extremely rare, were equally prevalent for people vaccinated with AstraZeneca’s vaccine compared to those who got Pfizer’s product. But abnormally low platelet levels were more common among people who got AstraZeneca’s vaccine.