Australia's 25 million people could begin receiving doses from January but there were "no guarantees", he said
Australia says it will secure almost 85 million doses of a coronavirus vaccine if two promising trials prove successful.
Prime Minister Scott Morrison said the country had struck two deals that would allow free doses to be rolled out in 2021 if they were approved for use, reports BBC.
Morrison estimated the cost to be $1.24bn.
Australia's 25 million people could begin receiving doses from January but there were "no guarantees", he said.
"However the agreement puts Australia at the top of the queue, if our medical experts give the vaccines the green light," the prime minister said.
One vaccine is from Oxford University and pharmaceutical company AstraZeneca, while the other is a local one from the University of Queensland and CSL. Both would most likely require people to take two doses.
Australia has recorded more than 26,000 coronavirus cases and 769 deaths, most in the past two months after an outbreak in Victoria.
The state announced on Sunday it was extending its strict lockdown for another two weeks, before gradually easing restrictions.
Under the plan, people in Melbourne will not be able to visit other households for group gatherings until at least late November.