Two very rare kinds of venous thromboembolism have affected a small number of people under the age of 50 after COVID-19 vaccination, regulators reported yesterday.
Medicines regulators in the UK and Europe said the incidents did not justify halting vaccination – and European governments acted on their advice to resume programmes today.
The European Medicines Agency said that, overall, vaccination with the Oxford/AstraZeneca vaccine is linked with reduced incidence of thromboembolism.
Its analysis found five cases of disseminated intravascular coagulation amongst recipients under the age of 50 – five times the expected number.
There were a further 12 cases of cerebral venous sinus thrombosis, nine times the expected number. Amongst these 17 cases there have been nine deaths.
The EMA’s safety committee called for heightened awareness amongst patients and doctors of these risks – but added: “The Committee was of the opinion that the vaccine’s proven efficacy in preventing hospitalisation and death from COVID-19 outweighs the extremely small likelihood of developing DIC or CVST.”
In the UK, Professor Sir Munir Pirmohamed, chair of the Commission on Human Medicines, said: “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, five possible cases of this have been reported to us so far, after 11 million 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.”
The World Health Organisation yesterday warned of the continued threat to Europe from the pandemic as the continent approached its one millionth recorded death from the virus.
It praised vaccination programmes but said they would not be enough to eliminate the virus and its threat.
WHO regional director Dr Hans Kluge also declined to criticise countries that have suspended use of the Oxford adenoviral vaccine.
He said: “It is testimony to strong surveillance and regulatory mechanisms. In vaccination campaigns, it is routine to signal potential adverse events. This does not necessarily mean that the events are linked to the vaccination.
“Venous thromboembolism is the third most common cardiovascular disease in the world. It happens in populations regardless of whether they are vaccinated or not. COVID-19 vaccination will not reduce illness or deaths from other causes.
“As of now, we do not know whether some or all of the conditions have been caused by the vaccine or by other coincidental factors. WHO is assessing the latest safety data, and once completed, the findings will be made public. At this point in time, however, the benefits of the AstraZeneca vaccine far outweigh its risks – and its use should continue, to save lives.”
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