The risk of thrombosis is higher in those vaccinated with AstraZeneca than in the general population

A new study published in The British Medical Journal shows slightly increased rates of vein clots among AstraZeneca vaccinees compared to rates expected in the general population. However, the researchers stress that the risk of such adverse events is considered low.

This work, carried out by researchers from Denmark and Norway, has compared the national rates of blood clots and related conditions after vaccination with AstraZeneca with those of the general population of both countries. Specifically, their results are based on 280,000 people between the ages of 18 and 65 who received a first dose of the vaccine in Denmark and Norway from February 2021 to March 11.

Analysis of the data found 59 blood clots in the veins compared to the 30 expected, which corresponds to an excess of 11 events per 100,000 vaccinations. This included a higher than expected rate of clots in the veins of the brain, known as cerebral venous thrombosis (2.5 events per 100,000 vaccinations). However, they did not find an increase in the rate of arterial clots, such as heart attacks or strokes.

Despite the registered trend, the authors emphasize that the absolute risks of venous thromboembolic events described are small, and that the results must be interpreted in the context of the benefits of vaccination against Covid-19 both at the societal and individual level. . In addition, they explain that the study carried out is observational, so it cannot establish a cause, but only a correlation.

Denmark and Norway have suspended vaccination with AstraZeneca

Denmark and Norway are two of the European countries that have suspended vaccination with AstraZeneca doses. The first has done so indefinitely and has included the Janssen vaccine, which also has thrombosis as a rare side effect. And the second, has postponed the decision to continue with AstraZeneca until May 10.

Both countries agree with the European Medicines Agency that the serum developed by Oxford is safe. However, the balance between risk and benefit modulates depending on the