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Risk of suffering serious blood clot after AstraZeneca jab doubles in fortnight

Coronavirus vaccines being prepared at Salisbury Cathedral, Wiltshire.  - Steve Parsons /PA
Coronavirus vaccines being prepared at Salisbury Cathedral, Wiltshire. - Steve Parsons /PA

The risk of suffering a serious blood clot after the AstraZeneca jab has doubled in a fortnight, new figures show, but the British regulator said the benefits still outweighed the risks for the vast majority of people.

New data from the Medical Healthcare products and Regulatory Agency (MHRA) show cases have risen from 79 to 168 since April 8, and deaths from 19 to 32.

The risk of getting a blood clot has also gone up from one in 250,000 to around one in 126,600 – or a rise of four in a million to 7.9 in a million.

Earlier this month the Joint Committee on Vaccination and Immunisation (JCVI) advised that under-30s should be offered an alternative to the Oxford jab, because the risk no longer outweighed the benefits for younger people.

A source close to JCVI said the committee would be reviewing the new data carefully this week, to assess whether the risk was also still worth the benefit for older groups now that the chance of getting a blood clot had risen.

However, some experts warned that the extra cases may be a result of “observer bias” where more people were reporting cases since the issue was brought to light.

Adam Finn, Professor of Paediatrics, at the University of Bristol, said: “There is now a very high level of awareness of this syndrome amongst the public and clinicians throughout the country and cases are being reported reliably and quickly but there are also cases that occurred previously now being recognised and reported as well.

“I would expect the true number of cases per million doses of vaccine to become clear fairly soon as these reports stabilise but it is already clear that it is going to remain a very rare event.”

On Thursday, the MHRA insisted that the benefits still outweighed the risks, and said although the incidence rate had increased, the number of cases remained extremely low given that over 23 million doses of the AstraZeneca vaccine have been administered.

Dr June Raine, the MHRA chief executive said: “Over 43 million doses of vaccines against Covid-19 have now been administered in the UK, saving thousands of lives through the biggest vaccination programme that has ever taken place in this country.

“No effective medicine or vaccine is without risk. These specific kinds of blood clots with low platelets reported following the AstraZeneca vaccine remain extremely rare and unlikely to occur. The benefits of the vaccine continue to outweigh the risks for the vast majority of people.

“It is still vitally important that people come forward for their vaccination when invited to do so.”

However, the MHRA urged people to seek medical advice urgently if they experienced a severe headache from around four days of vaccination, which does not get better with painkillers and feels worse when lying down or bending over.

They also warned to get help if headaches were accompanied by blurred vision, confusion, difficulty with speech, weakness, drowsiness or seizures.

And people were also asked to look out for a rash that looks like a small bruise or bleeding under the skin, shortness of breath, chest pain, leg swelling and persistent stomach pain.