Researchers at the University of Queensland have chosen a vaccine candidate for pre-clinical work while a US team is gearing up for trials, but more are needed.
"Whilst you have something in the lab that looks good, either you can't actually get it to generate the outcome in a human being that you want, or it proves not to be safe or it proves hard to manufacture," Ms Halton told ABC radio on Monday.
"So you need a series of candidates to ensure you end up with one, or preferably more, actual vaccines."
But a potential vaccine was still 12 months away if "absolutely everything went optimally".
It would then take "many, many months to produce the hundreds of millions of doses that will be needed for this vaccine", Ms Halton added.
The federal government has put $2 million towards a local fund to develop a vaccine and has so far pledged less than $5 million to CEPI.
About 75 Australians have tested positive to the coronavirus, with expectations the figures will climb further, and three people have died.
There are growing concerns some people aren't isolating themselves properly despite showing symptoms of a COVID-19 infection.
A Hobart student went to two nightspots and to work at a hotel despite being told to stay home and await the results of a test for the coronavirus.
A woman in Perth went to an orchestra concert and a Melbourne doctor treated patients while experiencing cold-like symptoms.
The country's peak medical body says any confusion people have about how to respond could be cleared up by letting Australia's Chief Medical Officer Brendan Murphy take the lead on information about the crisis, rather than politicians.
"Leadership from the chief medical officer is essential at this time and obviously he can direct and influence the decisions made by the chief health offices in respective states," Victorian AMA president Julian Rait said.
"We ask the government to respect the leadership we have and withdraw and not insert themselves into these debates and discussions without adequate knowledge."
Most of the confirmed coronavirus cases are in NSW, where the count is 40.
Two of the three deaths have also occurred in NSW. All of the victims were elderly people aged 78, 82 and 95.
The infected people either contracted the virus through person-to-person contact in Australia or during their travels overseas before returning home.