As Australians grapple with the mixed messages coming from on high about who should and who should not get the AstraZeneca jab, scientists are working to understand and eliminate the rare blood clotting problem.
A German researcher believes he has isolated the cause of the reaction, known as thrombosis with thrombocytopenia syndrome (TTS), or “clotting with small platelets” syndrome, which affects about 1 in 100,000 recipients of the AstraZeneca jab globally.
That extremely rare TTS response has caused two deaths in Australia from at least 64 cases. Last week, another woman died in England five weeks after receiving her first AstraZeneca shot in Australia.
AstraZeneca is now not recommended for Australians aged under 60.
Experts stress the statistical insignificance of 64 cases of TTS from about six million jabs, but some Australians feel it’s a risk not worth taking and are waiting it out for a Pfizer jab, although the over-60s have little choice if they want a vaccination.
Read more: Should I take AstraZeneca?
Professor Rolf Marschalek, of Frankfurt’s Goethe University, believes the AstraZeneca vaccine can be tweaked to fix the issue.
He has been leading studies into the rare vaccine response since March, the Financial Times reports. Prof. Marschalek says the blood clots are caused by the vaccine’s delivery method used to trigger an immune response.
The adenovirus vectors – the common cold virus – that AstraZeneca and Johnson & Johnson vaccines use to deliver the DNA instructions go right to the heart of the cell nucleus, while Pfizer and Moderna’s mRNA adenovirus vectors drop off the code to the cell fluid outside the nucleus.
If you have a degree in microbiology, that’s not surprising as DNA, which is the double-helix blueprint from which all biological life is created, functions within the nucleus, while RNA functions in cell fluid outside the nucleus.
If you don’t have a degree in microbiology, messenger RNA (mRNA) copies portions of genetic code and transports them to ribosomes, which are the cellular factories that produce proteins from this code.
And it’s a spike protein attaching the COVID virus to host cells that both vaccines are targeting.
Prof. Marschalek has observed AstraZeneca’s spike protein DNA splitting inside the nucleus, 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 1 in 100,000 people.
“When these … virus genes are in the nucleus, they can create some problems,” Prof. Marschalek told the Financial Times.
Read more: COVID jab safer than aspirin
The instructions for the spike protein in the Johnson & Johnson shot were already less prone to splitting than in the AstraZeneca jab, making the reaction less common, according to Prof. Marschalek. In the US, eight of 7.4 million recipients of the Johnson & Johnson shot have reported blood clots.
“[Johnson & Johnson] is trying to optimise its vaccine now,” 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.”
Some scientists have cautioned that Prof. Marschalek’s theory is one among many, and that further research is needed to substantiate his claims.
“There is evidence missing to show the causal chain from the splice … of the spike protein to the thrombosis events,” said Johannes Oldenburg, professor of transfusion medicine at the University of Bonn.
“This is still a hypothesis that needs to be proven by experimental data.”
The good news is that doctors in Australia have been able to identify possible cases of TTS quickly as more has been learnt from cases around the world.
Most cases have been successfully treated and the already low death rate from the syndrome is dropping further, said Dr Indu Singh, an associate professor of haematology at Griffith University.
Read more: Investigating vaccine side-effects
“The treatment for it is very well established and it is not something that always kills the patient,” Dr Singh said. “We know what to look for, and as long as we know about it, we are aware of it, it’s treatable, and the treatment is advanced.”
Anyone who has been vaccinated should seek immediate medical attention if they develop any of the following symptoms: severe or persistent headache or blurred vision, shortness of breath, chest pain, leg swelling or persistent abdominal pain, and unusual skin bruising or pinpoint round spots beyond the site of vaccination.
The most common time period for the onset of TTS symptoms is four to 30 days after vaccination.
Were you on high alert after receiving your AstraZeneca shot? Do you have any concerns about getting the second jab? Share your view in the comments section below.
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