Casablanca – A recent study conducted by the British Medical Journal found that the risk of thrombosis — blood clots that block blood vessels — after an AstraZeneca vaccine was higher than after a Pfizer/BioNTech vaccine.
“After a first dose of the AstraZeneca vaccine, there is a 30% higher risk of thrombocytopenia compared to a first dose of the Pfizer vaccine,” the study noted, adding that this risk is rare.
Although their frequency remains very low (with 862 cases for more than one million people vaccinated) the study confirmed that these thromboses are more common after the AstraZeneca vaccine.
Although the thrombosis risk increased after the first dose, the study found no differences between the AstraZeneca and Pfizer vaccines after the second dose.
According to the research, the unusual blood clots in combination with thrombocytopenia were mostly reported in women under the age of 60.
As a result, several European countries restricted the use of adenovirus vaccines in younger age groups as a precautionary measure.
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Meanwhile, data on the Johnson & Johnson vaccine pointed to an increased risk, though it was not clear enough for the researchers to reach a firm conclusion.
The study concluded that these risks “should be considered when planning further immunization campaigns and future vaccine development.”
The study was conducted on health data from millions of patients across Europe and the United States.
In European countries, AstraZeneca and Johnson & Johnson vaccines have already been largely abandoned in favor of Pfizer/BioNTech and Moderna. In the United States, AstraZeneca has never been approved.
The British study confirmed that “all [anti-Covid] vaccines are safe and effective.”
