The coronavirus infection rate is tracking in a way that will not overrun the country's health system, Prime Minister Scott Morrison said.
Mr Morrison said authorities had been working on the modelling of expected infections in Australia in light of numbers to date, and would release the work on Tuesday.
It had shown that without the measures put in place 12 days ago, when venues were closed and social distancing rules imposed, infections would be double the current numbers, he said.
On Friday, Australia had 5350 coronavirus cases. Mr Morrison said that would have been 10,500 without the partial shutdown.
"You're saving lives, you're saving livelihoods. And if you want to know how much, you only have to look overseas and see what is happening in other developed countries around the world," he said.
Mr Morrison said if measures stayed in place and intensive care capacity was boosted as planned, with extra ventilators, the health system would hold up.
"The early news on some of this early modelling is that at the current rate, if we keep doing what we're doing, and we keep doing the work to upgrade our [intensive care] capacity and secure the extra ventilators and all the things we are doing right now, then right now that trajectory is promising. It is encouraging.
"But there are no guarantees, I want to express. This virus writes its own rules."
Chief Medical Officer Brendan Murphy said the growth rate was falling, with case numbers now growing at about 5 per cent a day, well down from the rates of more than 20 per cent a fortnight ago.
There were about 300 cases in Sydney, 60 in Melbourne, 30 in Brisbane and smaller numbers in other states where the infection source was not known.
"That means there are people who have COVID-19 or who are incubating it who don't know it," he said.
"We are quietly pleased with the direction we're going but we cannot stop because those community transmissions are growing."
Globally, cases have passed one million cases, and Professor Murphy said the true number was probably five or 10 times higher, given limited testing.
In Australia, while there were "certainly undetected cases", authorities were confident they had "a pretty good idea of the size of our outbreak", he said.
Australia has 5350 cases at 3pm on Friday, an increase of 217 cases, or just 4 per cent on the day before. Since Friday, March 27, cases increased by 2184, or 70 per cent.
The government has to date refused to release its modelling of expected virus cases, hospitalisations and deaths, despite other countries openly sharing modelling based on the same information and despite a growing chorus of calls from experts for the data.
On Friday, immunologist and former Australian of the Year Professor Ian Frazer called on the government on Friday to release the information, saying it was important to understand the basis of the decisions being made.
"Some of these decisions are quite strict and impose quite limiting rules on what we're allowed to do. So we really need to know the evidence that's being used to support these decisions is there and how it was derived," he said.
"No evidence base will be perfect, but it's better to understand how the evidence base was created than not at all."
It appears the newly crunched figures will finally be released on Tuesday.
- For information on COVID-19, please go to the federal Health Department's website.
- You can also call the Coronavirus Health Information Line on 1800 020 080
- If you have serious symptoms, such as difficulty breathing, call Triple Zero (000)
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