The risk of developing a brain clot is up to 10 times higher in people with Covid-19 than those who have had a vaccine.
Researchers from the University of Oxford estimated that the clot, known as a cerebral venous sinus thrombosis (CVST), is eight to 10 times higher in people who have coronavirus, compared to those who have had a Pfizer or Moderna jab.
There have been concerns over the blood clot risk with the AstraZeneca vaccine, and the team behind the research said the findings should be reassuring to those who have had – or are due to have – one of the Covid-19 jabs.
The research analysed the health records of more than 80 million people in the U.S., and looked at the number of CVST cases seen in the two weeks after testing positive for Covid-19.
They also looked at the number of CVST cases in the two weeks following the first dose of a coronavirus vaccine, and found that it was much rarer to develop the brain clot after the jab.
Around 39 in every million people had a brain clot within 14 days of being diagnosed with Covid-19, while that figure was much lower – four in one million – for those who had the jab.
The study also found that the brain clots were more common in those who already had cardiovascular disease, and 80 per cent of people who have CVST survive.
The researchers noted that there were no figures for the AstraZeneca vaccine as it has not been used in the U.S.