Scientists in Germany say they have found the cause of rare blood clots linked to the Oxford/AstraZeneca and Johnson & Johnson COVID-19 vaccines and believe the jabs could be tweaked to stop the reaction happening altogether, the Financial Times has reported. 

It quotes Rolf Marschalek, a professor at Goethe university in Frankfurt as saying that his research showed the problem was the adenovirus vectors that both vaccines use to deliver the genetic instructions for the spike protein of the Sars-Cov-2 virus into the body. 

The delivery mechanism means the vaccines send the DNA gene sequences of the spike protein into the cell nucleus rather than the cytosol fluid found inside the cell where the virus normally produces proteins, the newspaper said.

Once inside the cell nucleus, certain parts of the spike protein splice, or split apart, creating mutant versions, which are unable to bind to the cell membrane where important immunisation takes place. The floating mutant proteins are instead secreted by cells into the body, triggering blood clots in roughly one in 100,000 people, according to Marschalek’s theory.

In contrast, mRNA-based vaccines, such as the jabs developed by BioNTech/Pfizer and Moderna, deliver the spike’s genetic material to the cell fluid and it never enters the nucleus. 

Marschalek told the newspaper there is a straight forward “way out” if the vaccine developers can modify the gene sequence that codes for the spike protein to prevent it splitting apart. 

J&J had already contacted Marschalek’s lab to ask for guidance and was looking at ways to adapt its vaccine to prevent splicing, he said.