German scientists identify possible cause of vaccine blood clots

Scientists in Germany believe they have discovered why the Oxford-AstraZeneca and Johnson & Johnson coronavirus vaccines cause potentially fatal blood clots in rare cases, and claim the issue can be fixed with a minor adjustment.

The authors of a new study claim their findings show that it is not the key component of the vaccines that cause the clotting, but a separate vector virus that is used to deliver them to the body.

Both the AstraZeneca and Johnson & Johnson jabs use a modified adenovirus, similar to the common cold virus, to deliver the spike protein of SarsCov2, the virus that causes Covid-19.

The scientists claim the delivery mechanism means the spike protein is sent into the cell nucleus rather than the cellular fluid, where the virus usually generates proteins.

In rare cases, they argue, parts of the spike protein can splice inside the nucleus, creating mutant versions which do not bind to the cell membrane where immunisation takes place, but are secreted into the body, where they can cause blood clots.

Dangerous clots in the brain have been recorded in 309 cases out of 33 million people who have received the AstraZeneca vaccine in the UK, and there have been 56 deaths.

“The adenovirus life cycle includes ... the entry of the adenoviral DNA into the nucleus, and subsequently gene transcription by the host transcription machinery,” the scientists claimed in a preprint of the study released this week.

“And exactly here lies the problem: the viral piece of DNA… is not optimised to be transcribed inside the nucleus.”

But Prof Rolf Marschalek of Frankfurt’s Goethe University, the leader of the study, claims the issue can be easily fixed by modifying the spike protein to prevent it splitting.

“With the data we have in our hands we can tell the companies how to mutate these sequences, coding for the spike protein in a way that prevents unintended splice reactions,” Prof Marsalek told the Financial Times.

He claimed Johnson & Johnson has already been in contact with his lab about a potential fix, but said he had not spoken to AstraZeneca.

“They never contacted us so we never spoke to them, but if they do I can tell them what to do to make a better vaccine,” he said.

Prof Marschalek’s claims are only one of a number of hypotheses currently being explored on why the jabs cause blood clots in some people.

A rival German study led by Prof Andreas Greinacher of Greifswald University Hospital claimed the clots were being caused by EDTA, a chemical used as a preservative in the AstraZeneca vaccine.

In a two-step process, the vaccine can cause an overreaction by the immune system in some people which causes too many platelets to form in the blood, Prof Greinacher argues.

EDTA can cause the cells in blood vessels to become “leaky”, causing platelets and proteins to flood through the body, triggering a massive immune reaction that can cause the blood clots.

“There is, in my opinion, rock-solid evidence,” Prof Greinacher claimed in April.

EDTA is not listed as an ingredient in the Johnson & Johnson vaccine but Prof Greinacher said he believes the phenomenon may be common to all vector vaccines.

A third German study released in preprint this week by scientists at Ulm University Medical Centre claims to have found unusually high levels of proteins in the AstraZeneca vaccine which it is theorized could be behind the clots.

“The often-observed strong clinical reaction one or two days after vaccination is likely associated with the detected protein impurities,” the authors of the study wrote.

The type of proteins involved “are known to affect innate and acquired immune responses and to intensify existing inflammatory reactions,” Prof Stefan Kochanek, the study leader, said. “They have also been linked to autoimmune reactions.”