Scientists in Germany and Norway said March 19 they identified a potential link between AstraZeneca's vaccine and reports of blood clots, The Wall Street Journal reported.
Two teams of medical researchers independently found that the vaccine could trigger an autoimmune reaction causing blood to clot in the brain.
"Nothing but the vaccine can explain why these individuals had this immune response," Pål André Holme, MD, PhD, a professor of hematology and chief physician of the Oslo University Hospital in Norway, told the Journal.
Andreas Greinacher, MD, professor of transfusion medicine at the Greifswald University Clinic in Germany, told the Journal that "very, very few people will develop this complication," and that if they do, "we now know how to treat the patients."
AstraZeneca declined to comment to the Journal, pointing to a March 18 statement saying an analysis of tens of millions of its vaccination records didn't show that the blood clots occurred any more frequently than would be expected in the general population.
Roughly 17 million people in the European Union and the United Kingdom have received AstraZeneca's vaccine, CNN reported March 19. Of those, AstraZeneca said March 14 that there were 15 events of deep vein thrombosis and 22 events of pulmonary embolism reported as of March 8.
More than 30 vaccine recipients were diagnosed with cerebral venous sinus thrombosis, according to the Journal. Most of those people were women under age 55. In Germany, 13 cases of cerebral venous sinus thrombosis were reported among roughly 1.6 million people receiving the vaccine. Twelve patients were women, and three died, the Journal reported.
Germany, France and Italy resumed using the AstraZeneca vaccine March 19, with an added warning that it could be linked to blood clotting, according to the Journal. More than two dozen European countries had stopped distributing the vaccine after the reports of blood clots.
The Medicines and Healthcare Products Regulatory Agency in Britain said the benefits of the vaccine continue to outweigh the risks because of the "extremely rare rate of occurrence" of the blood clots and because a link to the vaccine is unproven. The agency added that anyone with persistent headaches or bruising around the vaccination site after a few days should seek medical attention, the Journal reported.
The World Health Organization, U.K. health authorities and European Medicines Agency have all voiced support for the vaccine, according to CNN.
AstraZeneca has contracts to deliver 300 million doses of its vaccine to the U.S., CNN reported. The drugmaker is expected to apply for emergency use authorization with the FDA in the next few weeks.
The U.S. announced March 19 that it will send 2.5 million doses of AstraZeneca's vaccine to Mexico and 1.5 million doses to Canada. Tens of millions of AstraZeneca vaccine doses have been purchased by the U.S. and are sitting in manufacturing facilities.
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