Scientists in Germany claim to have cracked the cause of the rare blood clots linked to the Oxford/AstraZeneca and Johnson & Johnson coronavirus vaccines and believe the jabs could be tweaked to stop the reaction happening altogether.

Rolf Marschalek, a professor at Goethe university in Frankfurt who has been leading studies into the rare condition since March, said his research showed the problem sat with 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, Marschalek and other scientists said in a preprint paper released on Wednesday.