"We don't have global distribution for a vaccine of this type. The critical thing is it requires ultra-refrigeration and that can be difficult to maintain,"he said.

Opposition health spokesman Chris Bowen said Australia's supply chain had never done that kind of work before.

"Minister Hunt only issued tenders last week to co-ordinate the distribution of vaccines across the country to deliver on varied temperature requirements,"he said."We've been late to the party with our supply deals. Now the vaccines are almost here. We need more detail about how we get them into people's hands."

Mr Hunt said Australia was planning for an initial rollout of the COVID-19 vaccination program within the first quarter of next year. It was preparing for temperature requirements ranging from 8 degrees to -70 for each of the vaccine candidates.

The government's deal with Pfizer/BioNTech is for 10 million doses. Because the vaccine requires two doses to be effective,it would cover 5 million people.

Mr Hunt said health and aged care workers,the elderly and the vulnerable would be the first to access a vaccine. If required,thedeal with Pfizer/BioNTech,as well as one for 40 million doses of the Novavax candidate,includes an option for the government to buy extra doses where supply is available.

"By securing access to multiple COVID-19 vaccines,the government is building a diverse global portfolio of vaccine candidates and giving Australians the best shot at early access to a vaccine,"he said.

Australia also has agreements to purchase the University of Oxford/AstraZeneca vaccine and a local candidate from the University of Queensland and CSL Ltd.

Professor Booy said the global community would have a better understanding of the Pfizer/BioNTech vaccine candidate's efficacy once it was rolled out,but the preliminary results were encouraging.

"It's very exciting and I can understand why the scientists involved are so excited,"he said.

Professor Tscharke said the vaccine was not an"overnight miracle",but 90 per cent efficacy was much higher than the 50 per cent bar that had been set for a workable COVID-19 vaccine.

"There is inevitably going to be some impact on infection and transmission,and that's the key thing we want to know:Will it protect people or will it stop the pandemic?"he said.