AZ jab: the Australian scientists unravelling clotting mystery

Australia researchers are unravelling the mystery surrounding the rare blood clotting disorder that has been linked to the AstraZeneca jab to understand why this reaction occurs.

Dr Freda Passam leads the Haematology Research Group at the Heart Research Institute. Picture: Supplied.

Australia researchers are working to unravel the mystery of the rare blood clotting disorder linked to the AstraZeneca vaccine in a bid to determine who is susceptible and what treatments are available.

A team of scientists at the Heart Research Institute in Sydney have begun a pilot study using blood samples on a device which looks like “a chip with an artificial vein in it” called an assay to simulate circulation and observe the results.

Freda Passam, who leads the haematology research group, said the tool enabled her team to monitor the way blood interacts with a vein to gain insight into thrombosis with thrombocytopenia syndrome, the cause of which has “dominated the international scientific community” since the invention of the vaccine.

“We have a fake vein that’s made out of the lining of cells that we have in our vessels, which is called endothelial cells, so they make a lining which is simulating a vein and then we flow blood over from a donor, individual or patient, under the influence of a pump,” Dr Passam said. “And it flows over as if it was circulation, and what we observe under the microscope is either inflammation or a clot happening so that is recorded over time and we have measurements … of how much the individual has clotted or inflamed that vein.”

Dr Passam said the study had begun with just 50 blood samples to see if researchers could pick up a reaction comparing healthy people and individuals with pre-existing clotting conditions, similar to the cases of TTS linked to the vaccine.

“We do know how healthy individual blood works in this system like how much it interacts with the vessel so we have our baseline so we have our healthy individuals and we have comparison groups which are patients who have developed clots in the legs or the lungs or different types of immune carbolic conditions,” she said.

Dr Passam said her team were aiming to complete the pilot within six months and hopefully scale up the study to include more participants, citing the global need for answers concerning the science behind why about one in 90,000 people experience this reaction.

“The real world implications is that people will have less fear because they are informed, first of all of the statistics of what is the risk, which is confirmed by (the Australian Technical Advisory Group on Immunisation) and the health authorities and the physicians, so the knowledge of the incidents are important,” she said.

“And then the knowledge that there are tests that could pick up the tendency to clot to guide them not to receive that particular vaccine or if they do they may have through a therapeutic agent that may help prevent the downstream effects of the clot.”

Dr Passam said despite the very rare chance of clotting linked to the AstraZeneca vaccine, which had caused ATAGI to recommend the jab only be given to those over 60 except for in the Greater Sydney region, she was a supporter of both vaccines.

“AstraZeneca, which has been given heavily in the UK, has managed to get the UK out of lockdown, and here we are still struggling, not being able to work, not being able to go out,” she said.

“It’s a decision a country has to make based on the reality it‘s facing … I think both vaccines are good and AstraZeneca has this rare risk of this clotting reaction, but both of them have rare incidents of general reactions – some adverse events have been noted with Pfizer too.”

Dr Passam said while the reason vaccine-related thrombosis occurred had not been established, there were many probable theories including that it was the result of an “immune response”.

“(The theory is) some individuals are susceptible and they make antibodies and react to the drug,” she said. “And those antibodies are then confused and they don’t just react against the vaccine, they also destroy the vessels and platelets and cause clots.”

The samples used in the study were taken by Royal Prince Alfred.

Despite more than 6 million AstraZeneca doses being administered, there have only been 90 confirmed or probably TTS cases.