UK backs continued use of AstraZeneca vaccine after five cases of rare blood clots

LONDON (Reuters) - Britain’s medicines regulator on Thursday gave its continued backing to AstraZeneca’s COVID-19 vaccine, saying the benefits outweighed the risks after finding there had been five cases of a rare brain blood clot among 11 million administered shots.

FILE PHOTO: A vial of the Oxford-AstraZeneca COVID-19 vaccine is seen at Basingstoke Fire Station, in Basingstoke, Britain February 4, 2021. REUTERS/Peter Cziborra

Britain’s Medicines and Healthcare products Regulatory Agency (MHRA) said that use of the vaccine should continue while the five reports were investigated, and one official said that the rollout would likely continue even if a link was proved.

Concerns about reports of blood clots, along with low platelet levels, have led to some European countries including Germany to pause the rollout of the shot while the cases were investigated by the European Medicines Agency (EMA).

The EMA announced later on Thursday that the vaccine was “safe and effective”, and also said the benefits outweighed risks, even if a link between blood clots in the brain and the shot could not be definitively ruled out.

“The Oxford jab is safe and the Pfizer jab is safe. The thing that isn’t safe is catching COVID which is why it’s so important that we all get our jabs as soon as our turn comes,” British Prime Minister Boris Johnson said at a news conference in Downing Street.

“As it happens I’m getting mine tomorrow, and the centre where I’m getting jabbed is currently using the Oxford/AstraZeneca vaccine ... and that is the one I’ll be having.”

June Raine, Chief Executive of the UK’s MHRA, said there was “no evidence that blood clots in veins is occurring more than would be expected in the absence of vaccination, for either vaccine,” referring to AstraZeneca and Pfizer shots.

Raine said there had been a very small number of reports of an extremely rare form of blood clot in the cerebral veins (sinus vein thrombosis, or CSVT) occurring together with lowered platelets soon after vaccination, and a review of the cases was ongoing.

“Given the extremely rare rate of occurrence of these CSVT events among the 11 million people vaccinated (with AstraZeneca), and as a link to the vaccine is unproven, the benefits of the vaccine in preventing COVID-19, with its associated risk of hospitalisation and death, continue to outweigh the risks of potential side effects,” she said.

The University of Oxford, which developed the vaccine, welcomed the determination of the MHRA and the EMA, adding that the rollout of the vaccines should continue to be monitored.

CVST is a rare form of stroke caused by a blood clot that prevents blood from draining out of the brain.

One of the five reported cases was fatal, MHRA Vaccine Safety Lead Philip Bryan said, adding that the cases were all among men aged between 19 and 59.

Asked if any cases had also been reported from the rollout of the Pfizer vaccine, Bryan said that while there had been two cases of sinus thrombosis, they had not been accompanied with the thrombocytopenia - low platelet levels - that had been specific characteristics of the reports among those given AstraZeneca shots.

“The specific cases we’re looking at is that combination of events (of CVST and thrombocytopenia)” he said.


The MHRA said anyone with a headache that lasts for more than four days after vaccination, or bruising beyond the site of vaccination after a few days, should seek medical attention.

But Munir Pirmohamed, Chair of the Commission on Human Medicines, in a statement suggested that even if a link between the clots and the vaccine was established, it likely wouldn’t halt Britain’s rollout.

“If we feel that there’s causal link then we may need to update the product information, but overall, I don’t think that would necessitate pause to any kind of vaccination programme,” he told reporters in a briefing.

Stephen Evans, at the London School of Hygiene and Tropical Medicine, said that COVID-19 itself was associated with similar symptoms, making causality hard to establish.

“A major problem is discerning whether there is a possibility that this was caused by COVID-19,” Evans told Reuters.

“Exactly these sort of conditions have been seen in patients with COVID-19 prior to the vaccines being available.”

Reporting by Alistair Smout and Guy Faulconbridge, additional reporting by Kate Holton, Estelle Shirbon, Paul Sandle and Kate Kelland; Editing by Nick Macfie and Elaine Hardcastle