MHRA finds no causal link between AZ vaccine and rare blood clots after UK death

On Thursday, Britain's medicines regulator announced it had identified five cases of a rare and serious brain blood clot among people who had received the AstraZeneca vaccine. One of those five had died. The cases involved men ranging in age from 19 to 59, all of whom developed cerebral venous sinus thrombosis—a condition in which blood cannot drain properly from the brain—alongside an abnormally low platelet count.

The Medicines and Healthcare products Regulatory Agency stressed that it had found no causal link between the vaccine and these clots. The condition itself, officials emphasized, occurs naturally in the population at extremely rare intervals. The five reported cases represented less than one in a million chance of developing this particular type of clot. By comparison, the risk of dying from Covid-19 for someone aged 40 to 49 stood at one in 1,000—a thousand times higher.

Dr. June Raine, the MHRA's chief executive, framed the regulator's updated guidance as a precautionary step while investigations continued. She acknowledged that mild flu-like symptoms—headache, chills, fever—remained among the most common side effects of all Covid vaccines, typically appearing within hours and resolving within a day or two. But she urged people to seek medical attention if they experienced a headache lasting more than four days after vaccination or bruising beyond the injection site appearing days later.

Phil Bryan, the MHRA's vaccine safety lead, acknowledged the agency took every reported suspected side effect seriously. He noted that the five cases represented a very specific and unusual form of blood clot, similar to some cases that had surfaced in Europe in the preceding week. What remained unknown, he said, was whether the vaccine had caused them. The regulator was working with experts and blood specialists to gather more information and determine causation.

Professor Sir Munir Pirmohamed, chairman of the Commission on Human Medicines, said his team had reviewed all available data and concluded there was no increased risk of peripheral blood clots based on current evidence. He recommended that people continue to accept the vaccine when offered.

The British findings came as other European nations grappled with similar reports. Germany had received seven reports of bleeding and severe cerebral venous thrombosis linked to low platelets, with three deaths among people aged 20 to 50. Six of those cases involved a specific form of sinus vein thrombosis, and all of those affected were younger to middle-aged women. Italy's health minister expressed hope that the European Medicines Agency, which was due to deliver its own assessment that same day, would provide the clarity and reassurance needed to resume vaccination campaigns across the continent.

The regulator's message was measured but clear: the events were extraordinarily rare, the investigation was ongoing, and the benefits of vaccination against a virus killing thousands remained vastly greater than the observed risk.