Two separate teams of scientists in Germany and Norway concluded that the AstraZeneca vaccine could cause an autoimmune reaction, which in turn causes thrombosis in a small number of patients. The problem could be treated using a blood thinner and immunoglobulin, the German research team determined.
The Norwegian researchers claim to have identified an antibody triggered by the AstraZeneca vaccine that caused cerebral venous sinus thrombosis in isolated patients.
The findings, which have not yet been peer reviewed, could explain why a limited number of patients in have had cerebral venous sinus thrombosis.
Researchers at the Greifswald Medical School in Northern Germany reached their conclusions after obtaining blood samples from six thrombosis patients who had received the AstraZeneca vaccine. The researchers are working to obtain further samples. They collaborated with researchers from Austria and the Paul Ehrlich Institute.
Researchers at the Oslo University Hospital in Norway reached similar conclusions.
AstraZeneca had denied a link between its vaccine and blood clotting, noting that there have only been 37 blood clot reports out of a pool of more than 17 million doses administered in the EU and the U.K. That figure falls below the background rate of thrombosis, the company concluded.
Most of the people suffering from the problem have been women under the age of 55. That fact has led France to constrain use of the vaccine to people over that age.
In related news, AstraZeneca has recently announced plans to seek emergency use authorization in the U.S.
A U.S. Phase 3 trial results found that the vaccine was 79% effective at preventing symptomatic COVID-19.
The data safety monitoring board identified zero safety concerns after a specific review of thrombotic events.