CSL will start manufacturing rival vaccines © Getty Images

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Australia has abandoned the development of a homegrown Covid-19 vaccine after several trial participants returned “false positives” for HIV.

Canberra insisted on Friday that the setback would not delay its vaccination programme and announced it had bought 31m extra doses of rival vaccines produced by AstraZeneca and Novavax.

The University of Queensland and pharmaceutical company CSL said their Covid-19 vaccine candidate would not progress to phase 2 and 3 clinical trials, owing to concerns that it would interfere with HIV testing procedures and dent public confidence.

However, they said there was no possibility the vaccine could cause infection with the human immunodeficiency virus, which if left untreated can lead to Aids, and routine follow-up tests confirmed there was no HIV present in trial participants.

Brendan Murphy, secretary of Australia’s health department, said the trial was abandoned owing to the risk that HIV false positives could undermine public confidence in the vaccination programme.

“It [the vaccine] was likely to work. 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, but it was a very, very good technology,” he said.

Canberra plans to begin rolling out its vaccination programme from March, arguing that its success in suppressing the spread of the vaccine meant it did not have to rush through vaccine approvals.

It has signed agreements to purchase four vaccines at a cost of A$3.3bn (US$2.5bn), including deals with UQ/CSL, AstraZeneca/University of Oxford, Novavax and Pfizer/BioNTech.

Scott Morrison, Australia’s prime minister, said the abandonment of the UQ/CSL vaccine would not delay the nation’s vaccination programme, as CSL would now start manufacturing rival vaccines sooner.

Canberra purchased 31m extra doses of vaccine to ensure the population was covered when UQ/CSL informed the government about the trials, he said.

“The net out-take of this is we are more likely to have the entire population vaccinated earlier rather than later by the ability to bring this manufacturing capability forward,” Mr Morrison told reporters.

CSL/UQ said the vaccine candidate, which was developed using a ground-breaking molecular clamp technology, elicited a robust response towards the Covid-19 virus and had strong safety profile.

But significant changes would need to be made to well established HIV testing procedures if the vaccine were to be rolled out, according to both organisations.

CSL/UQ said the problems related to the use of small fragments of a protein taken from HIV to create the molecular clamp, which holds the vaccine’s synthetic virus in place. Trial participants developed antibodies towards this protein, known as gp41, which interfered with certain HIV tests, they said.

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Paul Young, UQ vaccine lead, said it was possible to re-engineer the vaccine but the team did not have the luxury of time needed to complete this work.

“Doing so would set back development by another 12 or so months, and while this is a tough decision to take, the urgent need for a vaccine has to be everyone’s priority,” Prof Young said.

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