risk of thrombosis increases slightly with its application

There is only a slight increased risk of intracranial thrombosis In some populations after vaccination with the preparation for Covid-19 from AstraZeneca and the University of Oxford, confirm two studies published this Tuesday in “PLOS Medicine”.

In the first work, the team of William Whiteley, from the University of Edinburgh, analyzed the electronic medical records of 46 million adults living in England, of whom 21 million were vaccinated during the study period, from December 2020 to March 2021.

According to the results, in people under 70 years of age, a small increase was observed, specifically, in the rate of intracranial venous thrombosis after the AstraZeneca vaccine.

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This corresponded to an estimated excess risk of 0.9 to 3 per million (varying by age and sex) and was about twice the rate compared to unvaccinated people; The same effect was not observed after the preparation of Pfizer.

“We have been able to show that these risks only occur in people under the age of 70 with the Oxford-AstraZeneca vaccine and that the increased risk is extremely small: no more than a few people per million vaccinated,” Whiteley said.

In adults younger than 70 years, “the small increased risk of intracranial venous thrombosis and hospitalization for thrombocytopenia after first vaccination with ChAdOx1-S -AstraZeneca- is likely to be offset by the effect of the vaccines in reducing of mortality and morbidity from Covid-19,” the authors say.

In the second study, Steven Kerr and colleagues, also from the University of Edinburgh, linked data from December 2020 through June 2021 from multiple sources, including primary care, secondary care, mortality and virological tests, for more than 11 million people. people in England, Scotland and Wales.

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They compared the rate of cerebral venous sinus thrombosis events – a rare type of blood clot at brain– within 90 days prior to vaccination and within 4 weeks after the first dose of the AstraZeneca and Pfizer preparations.

The authors observed a slightly increased risk of events after vaccination with ChAdOx1-S, equivalent to one additional case per 4 million people inoculated, which was approximately double that before vaccination.

The study found no association between the Pfizer vaccine and venous sinus thrombosis.

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