Biotechnology giant CSL gave University of Queensland researchers a licence to push ahead with a now-abandoned COVID-19 vaccine to avoid a 12-month delay.

The brains behind the Australian-made COVID-19 vaccine knew they were taking a gamble when they decided to use harmless HIV fragments in their project and it hasn't paid off.

Future development of the University of Queensland/CSL vaccine has been abandoned, with participants in the phase one trials returning false-positive results for human immunodeficiency virus.

The vaccine candidate was shown to generate antibodies toward its molecular clamp, which comprises two fragments of a protein found in HIV.

These antibodies were being picked up in low levels in some HIV tests, eliciting false-positive results among all 168 trial participants who didn't receive the placebo.

Dr Andrew Nash, chief scientific officer of the biotechnology giant, stressed CSL's decision to shut down development was not made over safety concerns.

"There are a number of challenges in rolling out the vaccine and these challenges might have an impact on public confidence in vaccination programs more broadly," he told reporters on Friday.

"At this stage, and without more data, significant changes would need to be made to the well-established HIV testing procedures and that healthcare setting would need to change to accommodate the rollout of this vaccine."

Paul Young, head of the UQ's school of chemistry and molecular biosciences, said the problematic HIV fragments made up six per cent of the total vaccine and were "completely harmless".

"We choose it because it provided the greatest stability in earlier studies that we conducted and we did engineer it that the major antibody binding sites for that protein had been removed," Prof Young said.

"We didn't anticipate that we would have the problem that we subsequently encountered."

Pre-clinical animal studies didn't pick up the issue as the diagnostic assays to the vaccine are based on human immune responses.

Trial subjects were briefed on the possibility that vaccine-induced antibodies might show up in tests and it was included in their initial consent forms.

Despite this, CSL gave University of Queensland researchers a licence to forge ahead with the HIV-fragmented clamp to expedite development.

"Given the urgency of the need to respond to the pandemic, and the sort of risk mitigation that Paul and his team had considered in designing the clamp, we thought we couldn't delay at least 12 months ... that would be incurred if we used an alternate clamp," Dr Nash said.

"So we made a risk-based decision to support this program as they proceeded.

"These things are risky and I think the urgency and scrutiny under which these vaccine programs are being conducted have given the public a front and centre view of the challenges we face every day in drug development."

Prof Young said it would have taken upwards of 12 months to redesign the molecular clamp using another form of protein, putting his team well off the pace of other promising vaccine candidates expected to rollout in Australia early next year.