Prime Minister Scott Morrison said "a supply problem" has impacted the ability of the Australian government to hit coronavirus vaccine targets set earlier this year.
The Federal Government forecast four million doses would be administered by the end of March when it first announced the program at the beginning of the year.
"It is pure and simple. There were over three million doses from overseas that never came," Mr Morrison said.
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"And that's obviously resulted in an inability to get three million overdoses out and distributed through the network.
"I think it is really important that these points are made very clearly when we are talking about the rollout of the vaccine."
Mr Morrison confirmed today that as of April 5, there were 854,983 vaccines administered in Australia and of that there were 280,943 vaccines given to people through GP clinics, respiratory clinics and other federal agencies.
He said that was in addition to those done through age and disability facilities, which was more than 112,000.
Mr Morrison said CSL, the Melbourne-based company responsible for producing the AstraZeneca COVID-19 vaccine, was "ramping up" its production.
https://twitter.com/Fi_Willan/status/1379311564981854209?ref_src=twsrc%5EtfwHe said vaccine testing would take time.
"Now, as CSL are ramping up their production and their systems are becoming even more efficient as they get into the rhythm of their production systems, there is also the approvals that they must follow once batches are produced," he said.
"That involves both AstraZeneca internationally, it involves the TGA batch testing as well.
"I think it is very important that people understand the fill and finish process doesn't involve the little vial coming off the production line and then go straight to the courier and the GP or the hospital where states may be administering doses. [This] is not how it works.
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"The way it works is once the vials are produced, they have to go through an approval process and it is important because Australians need to be assured of these vaccines and that they are ticking all of the boxes.
"It is not just a matter of having the vaccine approved initially by the TGA, they have to test the batches as well.
"That is about Australians' safety, and I don't intend to rush the process and put people's health at risk."
Australia will 'work to the supply we have'
Mr Morrison said the speed of Australia's vaccine roll-out would be affected by factors such as potential disruptions of supply.
"In early January, we anticipated we would have 3.1 million vaccines," he said in response to a reporter's question about the nation's vaccine rollout.
"Those vaccines were not supplied to Australia, and that explains the difference between the numbers you are referring to, and we made that very clear back in February.
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"We made it clear that they were indicative figures that we were working to at that time based on the information that we had, so I think it is important that as the government puts information out about the program it will be subject to change from time to time.
"There will be factors that come into play, such as the disruption of supplies.
"That can occur, even with domestic production. We need to work to the supply we have.
"I think that is only reasonable to consider in that way. That is what we will continue to do."
