Around a third of reports of cerebral venous thrombosis (CVT) after COVID-19 infection were in people under 30.

Risk of blood clot after coronavirus is eight times higher than after Oxford-AstraZeneca vaccine – study

Risk of blood clot after coronavirus is eight times higher than after Oxford-AstraZeneca vaccine – study

Reuters::There is a much higher risk of brain blood clots from Covid-19 infection than there is from vaccines against the disease, British researchers said on Thursday, after the rollout of inoculations was disrupted by reports of rare clots.

AstraZeneca and Johnson & Johnson have both seen very rare reports of cerebral venous sinus thrombosis (CVST) linked to their vaccines. On Wednesday, the United States paused vaccinations using J&J’s shot while a link with clots was investigated, with Denmark ditching AstraZeneca’s shot over the issue.

British and European regulators have stressed that the benefits of vaccination outweigh the risks.

The risk of developing a blood clot after having COVID-19 is eight times higher than after being given the Oxford-AstraZeneca vaccine, according to a study by Oxford University.

Cerebral venous thrombosis (CVT) occurred in 39 in a million COVID-19 patients, compared with about five in a million people given the AstraZeneca jab.

In the study of over 500,000 coronavirus patients, the risk was reported to be around 100 times higher than normal after infection.

Numerous countries have limited use of the vaccine to certain age groups or paused its rollout – with Denmark even dropping the jab from its vaccination programme permanently – following reports of very rare cases of blood clots.

However, the Oxford study suggested around a third (30%) of the CVT reports after COVID-19 infection were in people under 30.

The risk of developing CVT after taking either of these vaccines is about 10 times lower than after being infected with coronavirus, the study suggests.

But the researchers said comparisons should be interpreted with caution because data is still being gathered.

Professor Paul Harrison, from the University of Oxford, said: “We’ve reached two important conclusions. Firstly, COVID-19 markedly increases the risk of CVT, adding to the list of blood clotting problems this infection causes.

“Secondly, the COVID-19 risk is higher than seen with the current vaccines, even for those under 30; something that should be taken into account when considering the balances between risks and benefits for vaccination.”

And Professor Sir John Bell, the university’s regius professor of medicine, told Sky News: “The best way, if you want to have a bad clotting problem, is to get COVID.

“And if you don’t get a vaccine you’re going to get COVID, and if you get COVID you’ll have a very, very much higher risk of getting a bad clotting problem.

“So, the clotting problems of the vaccine are pretty trivial compared to the real risks of getting clotting problems if you get COVID.”

A study of 500,000 Covid-19 patients found CVST had occurred at a rate of 39 people out of a million following infection, researchers said. That compares with European Medicines Agency (EMA) figures showing that 5 in a million people reported CVST after getting AstraZeneca’s shot.

The researchers said in a pre-print study that the risk of CVST was 8-10 times higher following Covid-19 infection than it was from existing vaccines for the disease.

“The risk of having a (CVST) after Covid-19 appears to be substantially and significantly higher than it is after receiving the Oxford-AstraZeneca vaccine,” Maxime Taquet of Oxford’s Department of Psychiatry told reporters.

The study was based on a U.S. health database, and so did not accrue new data on the risk of clots from AstraZeneca’s vaccine directly, as the shot is not being rolled out there.

Taquet said that the mortality rate from CVST was around 20% whether it occurred after Covid-19 infection or a vaccine, indicating the clots were the main risk factor.

Regulators had also observed low platelet levels in reports of vaccine side effects, but the researchers said data was limited on whether that was also the case in those reporting CVST after infection.

The researchers highlighted that Covid-19 was associated with more common clotting disorders than CVST, such as strokes, and that recent debate around vaccines had lost sight of how bad the disease itself could be.

“The importance of this finding is it brings it back to the fact this is a really horrible illness as a whole variety of effects including increased risk of (CVST),” John Geddes, director of NIHR Oxford Health Biomedical Research Centre.

The research team, from Oxford University, said they worked independently from the Oxford vaccine team which developed AstraZeneca’s shot.

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