Scientists claim to have identified the cause of rare blood clots which have been linked to some Covid-19 vaccines.
Concerns have been raised over the AstraZeneca and Johnson & Johnson vaccines, after some people developed blood clots after their jab, but German researchers have said the current jabs could be modified to make them safer for future patients.
What is causing the blood clots?
A research team at the Goethe University in Frankfurt claim, in a study not reviewed by experts, the rare blood clots are caused by “floating mutant proteins”, which can occur when a vaccine sends the spike protein of the Sars-Cov-2 virus into the wrong part of a cell.
Lead scientist Rolf Marschalek said the issue lies with the adenovirus vectors, which both the AstraZeneca and Johnson & Johnson vaccines use to send the spike protein into the body.
This method then sends the spike protein into the cell nucleus, rather than the cytosol fluid inside the cell. Once inside, parts of the spike protein then split apart creating mutant versions.
These mutations are unable to bind to the cell membrane, causing “floating mutant proteins” to be secreted by cells into the body instead.
Prof Marschalek believes these proteins are what could potentially trigger blood clots in a small number of people.
By comparison, researchers said that vaccines which use a different technology known as RNA (mRNA), including the Pfizer and Moderna jabs, only deliver the genetic material of the coronavirus spike protein to fluid found inside cells, rather than the nucleus.
The findings were published in a pre-print journal paper released on Thursday (27 May).
Can the problem be solved?
The blood clot problem has disrupted the rollout of both the AstraZeneca and Johnson & Johnson vaccines.
In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) has recommended against the AstraZeneca vaccine among people under the age of 40, while the Johnson & Johnson vaccine was halted in Europe last month, and was temporarily paused in the US in April.
The company has since resumed its rollout with a warning on its label.
Blood clots have been reported in just over 309 out of the 33 million people who have received the AstraZeneca vaccine in the UK, causing 56 deaths, while in Europe around 142 out of 16 million vaccinated people have experienced blood clots.
However Prof Marschalek believes the problem could be solved if vaccine developers can modify the sequence of the spike proteins to stop it splitting apart.
Speaking to the Financial Times, he said: “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 Marschalek said he had presented his lab’s findings to the German government’s Paul-Ehrlich Institute and to the country’s advisory body on vaccination and immunisation.
In a statement, Johnson & Johnson said: "We are supporting continued research and analysis of this rare event as we work with medical experts and global health authorities.
"We look forward to reviewing and sharing data as it becomes available."