SYDNEY (REUTERS) - A fresh outbreak of infections in Australia's coronavirus hot zone of Victoria eased further on Wednesday (Aug 19), while the country agreed a deal to secure a potential Covid-19 vaccine that it plans to roll out cost-free to citizens.

Australia has signed a deal with British drugmaker AstraZeneca to produce and distribute enough doses of a potential coronavirus vaccine for its population of 25 million, Prime Minister Scott Morrison said late on Tuesday.

"Should we be in a position for the trials to be successful, we would hope that this would be made available early next year.

If it can be done sooner than that, great," Morrison said on Wednesday.

All Australians will be offered doses but a medical panel will determine the priority list of vaccine recipients.

"Naturally you would be focusing on the most vulnerable, the elderly, health workers, people with disabilities in terms of the speed of roll out," Health Minister Greg Hunt told Sky News.

Health authorities would also have to take into account where the highest risk of transmission is and how the vaccine works in different age groups when deciding who should get it first, Victoria's chief health officer Brett Sutton said

Victoria on Wednesday reported 216 new daily cases in the last 24 hours compared with 222 a day earlier.

It reported 12 deaths compared with 17 on Tuesday.

"If it does work and it's 80 to 90 per cent effective, then absolutely it will be a game changer," Sutton said, although he cautioned that broad testing was still at a preliminary stage.

"So we shouldn't hang our hats on a single vaccine."

AstraZeneca last month said good data was coming in so far on its vaccine for Covid-19, already in large-scale human trials and widely seen as the front-runner in the race for a shot against the novel coronavirus.

The vaccine, called AZD1222, was developed by Britain's University of Oxford and licensed to AstraZeneca.

Morrison said Australia was also looking for other vaccine deals, including with the University of Queensland and its partner, Australian firm CSL.

CSL estimates first doses of the University of Queensland vaccine will be available for emergency use by the middle of 2021, Chief Executive Paul Perrault told reporters on Wednesday.

CSL said its first priority would be manufacturing the UQ vaccine, but it was also in talks to help AstraZeneca manufacture its vaccine.

Morrison said Australia is also talking to its Pacific neighbours, including Indonesia, Papua New Guinea and Fiji, about supplying vaccine.

A flare up in infections in Australia's second most populous state of Victoria forced authorities two weeks ago to impose a nightly curfew, tighten restrictions on people's movements and order large parts of the state's economy to close.

The southeastern state has seen a slowdown in new cases in recent days, allaying fears of a nationwide second wave of infections.

There were 12 deaths and 216 new infections in the past 24 hours, down from daily increases of more than 700 two weeks ago.

Despite seeing a surge of new infections in the past month, Australia has largely avoided the high casualties of other nations with just under 24,000 infections and 450 deaths from the virus.