Researchers at the University of Oxford said Thursday that the risk of developing rare blood clots is higher after being infected with COVID-19 than in vaccinated people.
The findings are coming in a new study published by the university, which helped develop the AstraZeneca vaccine which is now under scrutiny for possible links to a brain blood clot known as cerebral venous sinus thrombosis (CVST).
Comparing the number of CVST cases in the two weeks after a COVID-19 diagnosis and after the first dose of a vaccine, Oxford reports that the risk of developing blood clots is as much as 10 times greater after a COVID-19 infection than it is after a vaccination.
The researchers noted that compared to the Pfizer and Moderna vaccines, the risk of developing CVST is about 10 times higher, while the risk is about eight times higher compared to the Oxford AstraZeneca vaccination.
While the study noted that data on possible links between the vaccines and blood clots are still being assessed, Paul Harrison, head of Oxford’s Translational Neurobiology Group, said Thursday’s findings “ should be taken into account when weighing the balance between risks and benefits for vaccination. . ”
The study comes after a wave of countries have restricted use of the AstraZeneca vaccine to older age groups due to reports of blood clots.
On Wednesday, Denmark became the first European country to stop completely using the AstraZeneca shot after an investigation “Showed real and serious side effects,” said the Danish health authority.
A Safety Committee of the European Medicines Agency (EMA) said last week that there is a “possible link” between the AstraZeneca vaccine and blood clots, although it added that the benefits of the vaccination to protect against COVID-19 outweigh the risks.
The Oxford study included no data on the Johnson & Johnson shot, which was interrupted in the US at the recommendation of health authorities investigating six cases of blood clots among the 7 million people who received the shot.
An independent advisory group from the Centers for Disease Control and Prevention on Wednesday delayed making a recommendation on the Johnson & Johnson injection until there was more evidence of blood clots, preventing the distribution of one of three coronavirus vaccines federally approved for use. in an emergency in the US.