COVID-19 vaccine trials abandoned

Ben Hocking

3 years ago

Further trials for Australia’s leading COVID-19 vaccine have been abandoned after testing revealed that people given the vaccine produced false positives for HIV.

The University of Queensland/CSL vaccine had showed a “robust response towards the virus” and passed stringent safety tests, but trials were abandoned as it was thought the false positives for HIV would undermine faith in the vaccine.

In a statement to the Australian Stock Exchange (ASX), CSL said further trials would not go ahead after the phase one trial produced these results.

“The Phase 1 data showed the generation of antibodies directed towards the ‘molecular clamp’ component of the vaccine,” the statement explained.”These antibodies interfere with certain HIV diagnostic assays. The potential for this cross-reaction had been anticipated prior to the commencement of the trial.

“Participants were fully informed prior to their involvement that this could occur. Blood samples from study participants were tested after vaccination and it was found that these molecular clamp antibodies did cause a false positive on a range of HIV assays.

“Follow-up tests confirmed that there is no HIV virus present, just a false positive on certain HIV tests. There is no possibility the vaccine causes infection.

“It is generally agreed that significant changes would need to be made to well-established HIV testing procedures in the healthcare setting to accommodate rollout of this vaccine. Therefore, CSL and the Australian government have agreed vaccine development will not proceed to Phase 2/3 trials.”

Professor Paul Young, one of the lead researchers on the trial, said it was possible to re-engineer the vaccine to remove the issue that caused the HIV false positives, but that it would set development of the vaccine back by 12 months.

“I said at the start of vaccine development that there are no guarantees, but what is really encouraging is that the core technology approach we used has passed the major clinical test,” Prof. Young said. “It is a safe and well-tolerated vaccine, producing the strong virus neutralising effect that we were hoping to see.

“We will continue to push forward and we are confident that with further work the Molecular Clamp technology will be a robust platform for future vaccine development here in Australia and to meet future biosecurity needs.”

While this vaccine seems to have faltered, CSL is still working on the manufacture of 30 million doses of the Oxford/AstraZeneca vaccine, with the first doses to be released in Australia early next year.

CSL’s chief scientific officer Dr Andrew Nash said that the Australian government had recently ordered an additional 20 million doses of that vaccine.

Prime Minister Scott Morrison thanked the University of Queensland team for its work, but explained that the government never expected that all four vaccine candidates it selected would result in a viable vaccine.

“Our vaccine strategy, and our vaccine policy, had identified four vaccines that we believed – based on the scientific advice – had the potential to go through to the end of stage three trials and be available here in Australia,” Mr Morrison said.

“We are increasing our production and purchase of AstraZeneca vaccines from 33.8 million to 53.8 million, and we’re increasing our access to the Novavax vaccine from 40 million to 51 million.”

Mr Morrison explained that the announcement that the University of Queensland trials have been abandoned should increase confidence in the vaccine process.

“What you’re seeing here is the system at work, protecting Australians, and making good decisions in the public health interest,” he said.

Health minister Greg Hunt said that Australia now had one of the highest rates of vaccine purchases and availability to population in the world, with enough doses of the AstraZeneca and Novavax vaccines to cover the entire population.

“The final outcome from all of that is that there is the potential for slightly earlier completion of the vaccine rollout for Australians in 2021,” Mr Hunt said.

Secretary of the federal health department Professor Brendan Murphy explained while the University of Queensland vaccine was promising, no trial could go ahead if it was going to undermine public confidence.

“It was likely to work,” Prof. Murphy said. “But we knew that we didn’t want to have any issues with confidence, and this false-positive test may have caused some confusion and lack of confidence.”

Prof. Murphy also explained that it was unlikely that the other three vaccine candidates would run into similar problems as they were already further along with their testing and used different mechanisms.

“The Novavax platform is very different,” Prof. Murphy said. “It doesn’t use the same molecular clamp – it uses a different approach. There’s no reason why we would expect the same thing. And they’ve published their phase one studies, and they haven’t realised any of these sorts of issues.

“The AstraZeneca vaccine is more advanced in its development than UQ was, and because it’s now in production, by making more of it, we can bring forward whole-of-population coverage with the AstraZeneca vaccine much earlier.”

The Pfizer vaccine has also got phase three trial information and has been approved for use in the United Kingdom and Canada and an advisory panel to the US Food and Drug Administration (FDA) has recommended its emergency approval as well.

US President Donald Trump signed an executive order that the US government should not share any of the vaccine doses it had obtained until it had enough for “all Americans who choose to be vaccinated”.

However, it is not clear that the executive order would be legally binding on Pfizer, which is a multinational company with offices around the world, and the vaccine’s final stages are produced in Belgium.

Are you still confident that Australia will return to normal in 2021 with the three remaining vaccine candidates?

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