LONDON (Reuters) – There is a much higher risk of brain blood clots from COVID-19 infection than from vaccines against the disease, British researchers said Thursday, after the rollout of vaccinations was disrupted by reports of rare blood clots.
AstraZeneca and Johnson & Johnson have both seen very rare reports of cerebral sinus vein thrombosis associated with their vaccines. On Wednesday, the United States interrupted vaccinations with J & J’s injection while investigating a blood clot link, with Denmark dropping AstraZeneca’s shot on the matter.
UK and European regulators have stressed that the benefits of vaccination outweigh the risks.
A study of 500,000 COVID-19 patients found that CVST had occurred in 39 out of a million people after infection, researchers said. This is comparable to figures from the European Medicines Agency showing that 5 in million people reported CVST after receiving the injection of AstraZeneca.
The researchers said in a pre-print study that the risk of CVST was 8-10 times higher after COVID-19 infection than with existing vaccines for the disease.
“The risk of developing (CVST) after COVID-19 appears to be substantially and significantly higher than after receiving the Oxford AstraZeneca vaccine,” Maxime Taquet of Oxford’s Department of Psychiatry told reporters.
The study was based on a US health database, so no new data was collected on the risk of blood clots from AstraZeneca’s vaccine as the injection is not rolled out there.
Taquet said the death rate from CVST was about 20% regardless of whether it occurred after COVID-19 infection or a vaccine, indicating that the clots were the main risk factor.
A new Oxford study shows that the risk of rare blood clotting (CVT) is several times higher after contraction #COVID-19 than after vaccination.
CVT is also 100x more common after COVID-19 than usual.
More information ⬇️ https://t.co/bVUxemNpxQ
– University of Oxford (@UniofOxford) April 15, 2021
Regulators had also observed low platelet levels in reports of vaccine adverse reactions, but the researchers said data was limited as to whether that was also the case in those who reported CVST after infection.
The researchers emphasized that COVID-19 was associated with more common blood clotting disorders than CVST, such as strokes, and that the recent discussion about vaccines had lost sight of how bad the disease itself could be.
“The significance of this finding is that it goes back to the fact that this is a truly terrible disease, given a slew of effects including an increased risk of developing (CVST),” John Geddes, director of the NIHR Oxford Health Biomedical Research Center.
The research team, from the University of Oxford, said they were working independently from the Oxford vaccine team that developed the AstraZeneca shot.
(Report by Alistair Smout; edited by Bernadette Baum)
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