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Corona vaccination: Researchers find a possible cause for rare cerebral vein thrombosis

2021-12-02T14:54:19.759Z

In very rare cases, AstraZeneca and Johnson & Johnson vaccines cause dangerous blood clots. Researchers have identified further explanations as to why this could be.



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AstraZeneca's vaccine

Photo: GABRIEL BOUYS / AFP

The corona vaccines from AstraZeneca and Johnson & Johnson are only recommended in Germany for people aged 60 and over.

The reason for the adjustment of the vaccination recommendations was the increased incidence of blood clots in the brain in recently vaccinated people.

Since the very rare complication was known, scientists have been looking for the cause.

A team from Great Britain and the USA reported in a study published in the journal Science Advanced about further possible explanations.

Chain reaction of the immune system

The researchers therefore assume that the so-called platelet factor 4, which is part of the human coagulation system, plays a central role in the formation of blood clots. According to the analyzes, this is attracted and activated in the blood like a magnet by the adenoviruses used as vectors in the vaccines by AstraZeneca and Johnson & Johnson. This could set off a chain reaction that both forms clots and consumes platelets that are used to stop bleeding - and bleeding occurs at the same time.

This rare but serious complication is called TTS syndrome - thrombosis combined with thrombocytopenia (lack of platelets). The current safety report of the Paul Ehrlich Institute (PEI) shows that 189 cases of thrombosis with simultaneous thrombocytopenia have been reported there after vaccination with the AstraZeneca vaccine.

The preparations from AstraZeneca and Johnson & Johnson - and also the Russian Sputnik, which is not approved in Germany - belong to the so-called vector vaccines: The vector or transporter consists of adenoviruses that do not multiply, but part of the genetic information of the Sars-CoV-2 coronavirus be able to smuggle them into human cells, so to speak piggyback. These then briefly produce a fragment of the coronavirus, the so-called spike protein. As part of the natural immune response, the body then develops targeted defense mechanisms against the spike protein - and the vaccination makes you highly immune to Covid-19. AstraZeneca, Johnson & Johnson and Sputnik use various adenoviruses as vectors.

The researchers suspect that the body also attacks platelet factor 4 (PF4) with antibodies.

The cause could be the complex of PF4 and adenovirus, which the immune system classifies as foreign.

This "misplaced immunity" still has to be investigated in studies.

Alan Parker, one of the researchers at Cardiff University, told BBC News, referring to the latest study results, "What we have is the trigger, but there are many steps that must be taken next."

more on the subject

Cerebral vein thrombosis: How the AstraZeneca vaccination could lead to blood clotsBy Nina Weber

In March, researchers from the University of Greifswald published a study that also identified an autoimmune process as a likely mechanism of origin. At that time it was unclear what exactly triggered the formation of the antibodies: the strong inflammatory reaction after the vaccination or the vaccine itself, wrote the team led by Greifswald transfusion specialist Andreas Greinacher. With their current study, the British and US researchers have now made a further contribution to understanding the rare blood clotting disorder.

Just like the vaccines from Biontech and Moderna, the vaccines from AstraZeneca, Johnson & Johnson and Sputnik also protect against severe Covid-19 disease.

Those who become infected with the virus are at a much higher risk of developing thrombosis than those who have been vaccinated with vector vaccines.

mar / he

Source: spiegel

All tech articles on 2021-12-02

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