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Immunizations with AstraZeneca’s COVID-19 vaccine can lead to blood clots in very rare cases, according to new research published Friday in The New England Journal of Medicine.
This is the latest scientific indicator that the company’s shot is tied to the occurrence of blood clots that have so far been more likely to affect women; however, the number of people to develop the blood-clotting disorder is considered to be very rare.
U.S.-listed shares of AstraZeneca AZN UK:AZN were up 0.7% in trading on Friday.
The medical journal on Friday published two articles: one examining five health-care workers in Norway who had developed blood clots 7 to 10 days after receiving the first dose of the AstraZeneca vaccine, and the other written by German scientists, who examined 11 patients in Germany and Austria who had reported blood clots after receiving the shot. In this case, the blood clots appeared 5 to 16 days after vaccination.
Both articles refer to what they call “vaccine-induced immune thrombotic thrombocytopenia” (VITT) as the reason behind the rare blood-clotting disorder, with the German researchers suggesting that this should be how the disorder is named.
“The findings of our study indicate that VITT may be more frequent than has been found in previous studies in which the safety of the ChAdOx1 nCoV-19 vaccine has been investigated,” the Norwegian researchers concluded.
Since reports of sometimes fatal blood clots have emerged, European nations like France and Germany have halted use of the vaccine, which was developed in partnership with the University of Oxford. This vaccine has not been authorized in the U.S., though the company recently said it planned to seek emergency-authorization from the Food and Drug Administration.
The European Medicines Agency said Wednesday that the blood clots should be listed as a very rare side effect for the vaccine, and the World Health Organization said later the same day that it’s “plausible” there is a tie between the vaccine and reports of blood clots, though it had not been confirmed at that time.
AstraZeneca’s stock is down 0.2% for the year, while the broader S&P 500
SPX,
is up 8.5%.
