SYDNEY - Most countries with access to Covid-19 vaccines have been urgently rolling them out as quickly as possible, but Australia has taken a different approach and is delaying vaccinations for as long as it can.

Australia wants to understand how the vaccine has been working in other parts of the world

Despite securing access to massive stocks, Australia has decided to take a "watch and wait" approach and wants to understand how the vaccine has been working in other parts of the world before beginning its immunisations.

The federal government plans to start its mass immunisation campaign in mid- or late-February. It will initially vaccinate front-line health workers, staff at quarantine facilities and other workers who deal with international arrivals, and people living in aged care homes or who have a disability.

The aim is to vaccinate four million of Australia's 25 million residents by the end of March and the entire population by October.

Prime Minister Scott Morrison said on Wednesday (Jan 21) that the government was taking its time with its roll-out and - unlike countries in the grip of serious outbreaks - had no need to risk cutting corners.

"We've got a range of countries overseas that have already started vaccination programmes," he told 2GB Radio. "There's a real desperation to the programme over there. That's not the case here. It means that we can protect Australians with this vaccine and make sure we get it right, learn from that."

The aim is to vaccinate four million of Australia's 25 million residents by the end of March and the entire population by October.

Prime Minister Scott Morrison said on Wednesday (Jan 21) that the government was taking its time with its roll-out and - unlike countries in the grip of serious outbreaks - had no need to risk cutting corners.

"We've got a range of countries overseas that have already started vaccination programmes," he told 2GB Radio. "There's a real desperation to the programme over there. That's not the case here. It means that we can protect Australians with this vaccine and make sure we get it right, learn from that.""We've got to start straight away. We can't delay this," he told The New Daily news website.

"The global situation, the gravity of what's going on, doesn't allow us to wait. The vaccines have got to get the tick, but once it does, it has to go out."

The Government is sticking to its plan for a February roll-out, though it had initially planned to wait until March.

But a separate debate has broken out in Australia about which vaccine to use.

Australia has secured 53.8 million doses of the AstraZeneca vaccine and 10 million doses of the Pfizer vaccine.Some experts have raised concerns about Australia's reliance on AstraZeneca's vaccine, saying it is less effective than that developed by Pfizer and Moderna and will not achieve herd immunity. The AstraZeneca vaccine is shown to provide 62 per cent or 90 per cent protection, depending on the dosage. The Pfizer vaccine has 95 per cent efficacy.

An infectious diseases expert, Dr Michelle Ananda-Rajah, from Monash University, said Australia should try to secure more doses of the Pfizer and Moderna vaccines.

"We need to pivot our strategy," she told ABC News.

"It's really about just ensuring that we provide for Australians the best possible vaccine... (AstraZeneca's vaccine) is just not going to confer herd immunity at a population level. We just don't believe that, based on our current data."

Australia plans to initially use its Pfizer doses to vaccinate vulnerable members of the population but to use the AstraZeneca vaccine - which is being made locally - for the bulk of the population.

The government has defended its use of the AstraZeneca vaccine, saying it had been shown to be 100 per cent effective at preventing severe disease, hospitalisation and deaths.

Australia's chief medical officer, Professor Paul Kelly, said it was more important to proceed with vaccines that were readily available and had more than 50 per cent efficacy than to wait for others that may have higher efficacy rates.

"The AstraZeneca (vaccine) is here, we don't need to queue for that," he told reporters earlier this month. "It will save lives. By using this vaccine, we'll be able to protect a large proportion of the population in Australia."