The coronavirus vaccine rollout in the UK has been vaunted and for good reason – it appears to be ushering in the end of the pandemic in Britain. However, AstraZeneca and Johnson and Johnson have been back into the fray this week after reports emerged of two fatalities linked to a rare blood clot disorder following vaccination. Why some vaccines cause rare blood events and others don’t has puzzled the scientific community.
Some of the instructions for making coronavirus proteins can be misread, potentially triggering blood clot disorders in a small number of recipients, they suggested.
According to Dr Rolf Marschalek, a professor at Goethe University who led the study, after entering the nucleus, parts of the spike protein splice or split apart and create mutant versions which are unable to bind to the cell membrane.
The spike protein is found on the surface of the virus that causes COVID-19. It facilitates the coronavirus’ entry into host cells.
These mutant versions then enter the body and trigger the rare blood clots, Dr Marschalek suggested.
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Marschalek told the Financial Times that the process is different with mRNA vaccines, such as those made by Pfizer and Moderna, because the genetic material of the spike protein is sent directly to the cell fluid and does not enter the nucleus.
The yet to be peer-reviewed study also suggests that those making vaccines using adenovirus vectors could alter the sequence of the spike protein “to avoid unintended splice reactions and to increase the safety of these pharmaceutical products.”
Johnson & Johnson, in an emailed statement to Reuters, 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.”
AstraZeneca declined to comment.
What are my chances of developing a blood clot?
It must be stressed that the blood clotting disorder is an extremely rare occurrence in people receiving a coronavirus vaccine.
According to the latest data, out of the 30.8 million doses of the University of Oxford/ AstraZeneca vaccine administered in the UK between 9 December 2020 and 5 May 2021, there have been over 260 cases of thrombosis with thrombocytopenia.
This is the equivalent of 10.9 cases per million doses.
The vast majority of events have been reported following the first dose and only eight after the second dose.
The latest MHRA guidance on COVID-19 vaccines and blood clots states that the risk is currently estimated to be around one in 100,000 for people over 50 and one in 50,000 for people aged between 18 and 49 years.
Nonetheless, for people aged between 18 and 49 the guidance states that “if you are offered the [University of Oxford/AstraZeneca] vaccination you may wish to go ahead after you have considered all the risks and benefits for you.”
Am I eligible to receive a coronavirus vaccine?
The NHS is currently offering the coronavirus (COVID-19) vaccine to people most at risk.
You can get the COVID-19 vaccine if:
- You’re aged 30 or over
- You’ll turn 30 before 1 July 2021.