Is blood clotting a side-effect of the AstraZeneca jab? Although reports of clotting associated with the jab give the impression of causation, health agencies insist the link is tenuous. The European Medicines Agency (EMA), AstraZeneca and UK-based Medicines and Healthcare products Regulatory Agency (MHRA) have stated the noted instances of clotting do not exceed those in the general population. AstraZeneca said in a statement: "Following a recent concern raised around thrombotic events, AstraZeneca would like to offer its reassurance on the safety of its COVID-19 vaccine based on clear scientific evidence. "Safety is of paramount importance and the Company is continually monitoring the safety of its vaccine.