The SMH spoke to a source involved in the trial who said although all participants had been told there was a remote possibility HIV markers could be found in tests during the trial, medical researchers had not expected it to occur.
Researchers previously said the vaccine was ahead of schedule and would be available to Australians by the end of 2021. Last month, UQ vaccine project co-leader Professor Paul Young said the early indications suggested there were minimal side effects to the jab.
Australia has entered into five separate agreements for the supply of Covid-19 vaccines, if they are proved to be safe and effective, including the UQ vaccine which is being developed in partnership with Australian global biotech company CSL.
Australia's Agriculture Minister David Littleproud said this morning's news shows why the government has taken the right approach.
"This is why we didn't put all our eggs in one basket," he told the Today programme. "This is why we made sure there were four contracts we signed to make sure that we got a vaccine and this is intrinsically very difficult science that UQ and around the world is trying to break.
"So it was important that we didn't just say, 'You are the winner', we actually spread our risk and made sure if there was a vaccine we got it and got it quickly.
"I think UQ, I wouldn't write them off yet but I think this backs what the government has done in making sure that we said we will spread our risk and we will make sure we have multiple agencies that are looking at this and gave us the vaccine that is safe. That is the main thing. We want a vaccine that is safe and gets us back to our real lives again."
A spokesman for the government told news.com.au earlier this week that there had positive developments across all of the candidates in recent weeks, and that Australia was still on course to start rolling out vaccines to the most vulnerable by March 2021.
It's anticipated that anyone who wants a vaccine in Australia will be able to get one by the end of 2021.
News.com.au has contacted UQ and the Health Department for comment.