The independent Covid-19 expert working group of the Commission on Human Medicines, together with leading haematologists, conducted a rigorous analysis of all available evidence regarding reports of blood clots (thromboembolic events) and Covid-19 vaccine AstraZeneca.
Our review has found that the available evidence does not suggest that blood clots are caused by Covid-19 vaccine AstraZeneca.
We have been closely reviewing all reports of blood clots in the vein (venous thromboembolism, or VTE) following vaccination. There is no evidence either that VTE is occurring more often in people who have received the vaccine than in people who have not, for either vaccine.
However, we will continue to closely monitor the reports where cerebral sinus venous thrombosis has occurred in conjunction with lowered platelets to understand whether there is any potential association. This type of blood clot can rarely occur naturally in unvaccinated people as well as in people with Covid-19 disease. In the UK, 5 possible cases of this have been reported to us so far, after 11m doses of Covid-19 vaccine AstraZeneca.
Further work with expert haematologists is under way to further understand the nature of these cases and whether there is a causal association with any of the vaccines. Given the extremely rare rate of occurrence of these events, the benefits of the AstraZeneca Covid vaccine, with the latest data suggesting an 80% reduction in hospitalisation and death from Covid disease, far outweigh any possible risks of the vaccine in the risk groups currently targeted in the UK.