Another 25 cases of blood clots reported in UK after AstraZeneca vaccine – but regulators say it’s still safe

Scientists believe they have uncovered why people who have recently had the AstraZeneca Covid vaccine have suffered blood clots

A handful of the millions of people who have received the vaccine in Europe have experienced the extremely rare complication.

While it is still uncertain whether this was directly caused by the vaccine, scientists in Europe say they have an explanation.

Two studies, in Germany and Norway, claim the shot may cause the body to activate its own platelets - blood cells which form clots to stop bleeding.

This causes the blood to thicken, leading to potentially deadly clots.

Noweigan professor Pål Andre Holme claimed this was the “most likely” cause.

'WEAK EVIDENCE'

But independent scientists said the theory is based on the "weakest evidence", and gave no further answers.

Millions of people across the world have had the AstraZeneca vaccine - developed by Oxford University - without any complications.

Regulators have stressed that the benefits of the jab, to prevent Covid deaths, far outweigh any potential risks.

European regulators say there is no overall increased risk of blood clots in people who get the shot, or that from Pfizer.

But it is unclear whether a very small number of brain blood clots - including five in the UK, one of whom died - were the result of the jab.

The condition, called CVST, occurred with low blood platelets and is an extremely rare combination of events.

It’s so rare, UK regulators at the MHRA said they did not know how often it happens in the general population.

ACCEPT JAB

While investigations continue, people have been urged to accept their vaccine offer when it comes.

If anyone experiences headaches or severe bruising after their jab, they should seek medical help immediately, experts have warned.

The German study, led by the University of Greifswald, looked at nine patients in Germany and Austria who had some form of blood clotting after one AZ shot, seven of whom had a blood clot.

They believe the phenomenon is similar to a rare disorder that occurs with a blood thinning drug called heparin.

Heparin can trigger the immune system to create antibodies that fire up the platelets.

This is called “heparin-induced thrombocytopenia (HIT)”, and can also be caused by other drugs, leading the scientists to believe it could be the case for the AZ jab, too.

Researchers said four people studied had these antibodies in the blood.

And 20 individuals who received the vaccine but did not develop clots did not have these antibodies.

'INSECURE CONCLUSION'

Adam Finn, professor of paediatrics at the University of Bristol, said the study had “several limitations” that make its findings less convincing.

For example, it was not investigated whether the patients had previously had Covid - a risk factor for blood clotting in itself.

He said: “The authors’ conclusion that the relationship with vaccination is causative seems insecure at this point and further information on incidence and mechanism in this and other populations is therefore urgently needed to resolve this question."