The UK medicines regulator has revealed that seven people who had received the Oxford / AstraZeneca Covid-19 vaccine died after recording the rare blood clotting events that resulted in precautionary restrictions on the use of the vaccine in several European countries.
The Medicines and Health Products Regulatory Agency told the Financial Times that it had received 22 reports of cerebral venous sinus thrombosis and eight reports of other thrombosis events that had been associated with low platelets, resulting in seven deaths of the 18.1 million people who received the AstraZeneca vaccine.
The unusual combination of blood clots and low platelet counts has already alarmed some groups of scientists in mainland Europe. Reports of similar incidents have caused France, Sweden, Finland, Canada and more recently Germany to recommend that younger people, who are much more likely to be affected by the disease, avoid the shot. In Norway and Denmark, the vaccine is still on hold.
The MHRA, the European Medicines Agency and the World Health Organization all said no evidence was found of a causal link between the vaccine and the disease. They recommended that governments continue to administer the vaccine.
The MHRA initially reported the new cases on Thursday, as part of a weekly update on post-vaccination yellow card events, although it did not discuss the deaths. Following this update, Downing Street said he would continue to assess the evidence as it was gathered, but that his advice and vaccination strategy remained unchanged.
“We remain absolutely confident in the vaccine,” he said.
Thirty cases of blood clots associated with a low platelet count is equivalent to approximately one in 600,000 people who have received the AstraZeneca vaccine. This was a large increase from the number of such incidents recorded in the previous MHRA report of March 22. This showed 4 cases of CVST and no deaths for the period January to March 14.
All of the reported cases were in people who had only received their first dose of the vaccine, the MHRA told the FT. “Of the 30 cases mentioned in our statement. . . unfortunately seven died, ”he said.
The UK has not seen any of the same incidents among people who received the BioNTech / Pfizer vaccine, the MHRA said.
CVST occurs when blood clots in the veins leading from the brain, which itself is a potentially life-threatening complication. In the most concerning cases, this has been combined with a problem called thrombocytopenia where a patient also has abnormally low levels of platelets, resulting in heavy bleeding.
In Norway, health officials have reported at least six such cases among 120,000 vaccine recipients, four of whom have died. In Germany, 31 cases have been reported after 2.7 million vaccinations, including 29 women aged 20 to 63 and two men aged 36 to 57. Nine of them died. In the UK, the MHRA did not provide information on age or gender for individual cases.
Dr June Raine, Director General of the MHRA, reaffirmed that “the benefits of the Covid-19 AstraZeneca vaccine in the prevention of Covid-19 infection and its complications continue to outweigh all risks and the public should continue to be vaccinated when instructed to do so ”.
Even if a causal link were to be established, some experts said it would still make sense to continue with vaccinations as incidents of blood clots seemed extremely rare.
“No medical intervention is ‘safe’ and the balance between benefits and risks is crucial,” said Professor David Spiegelhalter, chairman of the Winton Center for Risk at the University of Cambridge. “A one-month delay to vaccinate 500,000 people aged 44 to 54 should lead to about 85 serious cases requiring hospitalization, of which perhaps 5 would die.”
David Werring, professor of clinical neurology at UCL, said the incidence of CVST in the UK is normally around 5 to 15 cases per million people per year. “So the absolute risk of CVST after this vaccine remains extremely low, around 1.5 per million.”
The University of Oxford and AstraZeneca said their trials showed the vaccine to be safe and effective, and they continued to monitor side effects as the vaccine rolled out.