The British study, published in the British Medical Journal (BMJ), compared the medical data of 29 million people who received their first dose of Pfizer-Bionntech or Oxford-Astrazeneca between December 2020 and April 2021 with those of almost 2 millionof people who tested positive for coronavirus.

Concern for thrombi stopped the use of the Astrazeneca vaccine, but the researchers discovered that, although there is a "greater risk" of developing them after being vaccinated, this is "much less than that associated with SARS-COV infection- 2".

The risk of developing a venous thrombosis is almost 200 times higher with COVID-19 (12.614 additional cases among 10 million people) that with Astrazeneca (66 additional cases).

As for arterial thrombosis, there was no excess of cases for either vaccines, but 5 were counted.000 additional cases among 10 million people infected with the coronavirus.

Thus, people with the virus are more likely to suffer a stroke (1.699 additional cases of every 10 million people) than those vaccinated with Pfizer (143 additional cases).

"The vast majority of patients are perfectly well with these vaccines," the researcher who directed the study, Julia Hippisley-Cox, told the BBC, stating that the "very rare cases" of blood clots should be "placed in context".

This Epidemiology professor at Oxford also pointed out that the risk of developing blood clots is concentrated in "specific and short" periods with vaccines ("15 to 21 days after administration" with Pfizer for the stroke, "of8 to 14 days for thrombocytopenia with astrazeneca ") that after the spread of COVID-19, where the risk extends" more than 28 days after the infection ".

This study comes at a time when many countries - including the United Kingdom - have decided to reserve the Astrazeneca vaccine for an older population, due to the fear of thrombus.

English public health estimates that vaccines avoided more than 100,000 deaths in the United Kingdom, where pandemic has charged 132 thousand lives.

AFP