It's the one curve the government doesn't want to flatten.

Australians have enthusiastically embraced the government’s new contact tracing app, with more than 2 million people downloading and registering for COVIDSafe in just over 24 hours.

Health minister Greg Hunt revealed the top-line figure late on Monday, demonstrating strong take-up since registrations began on Sunday.

At just over 2 million registrations, the voluntary Android and iOS app now covers approximately eight percent of the population.

More than 870,000 downloads and registrations occurred between 6:00am and 7:30pm AEST.

The official count at 6:00am on Monday put the number of downloads and registrations at 1.13 million, though the first million occurred in five hours on Sunday night.

“We had hoped we might get to a million within five days, [but] we were lucky enough as a country to get there in five hours last night,” Hunt told 3AW on Monday morning.

 

The government wants 40 percent of the population to download the app to increase its effectiveness in the contract tracing process conducted by state and territory health professionals.

However, regardless of whether this occurs, the government will need to tweak the app so that it works in the background on iOS devices.

Without this fix, the 54 percent of the population with an iPhone will need to ensure the app is open - or open when the phone is locked - to log contacts.

Health department's chief information officer Daniel Keys on Monday said that it was unclear whether improvements by Apple, including through the proposed contact tracing API, would address the issues.

“It's unclear at this stage, so we’re working with Apple and Google on their functionality to ensure it can be consumed by the app to improve the app’s performance,” he said.

Keys also addressed questions on why the government had developed its own app using code from Singapore’s TraceTogether app instead of waiting for Google and Apple’s API.

He said the government had gone down the path of developing a contact tracing because the Google and Apple solution was still some time away, and would only be available to users with devices that can update their operating system.

“We moved forward to provide a capability that can support the government’s agenda to allow us to then introduce a capability that we can then build on when the Apple and Google functionality comes in,” he said.

“I’d also like to add that that capability that’s being built into their operating systems will only be available to those people who upgrade. 

“Now for some people, the phones will not handle an upgrade, so we need to cater from a diverse range of users out there and provide solutions for as many people as possible.”

Both Keys and Hunt also said the government would release the app’s source for independent scrutiny sometime in the next two weeks, though the Australian Cyber Security Centre would determine how much of it can be released.

Updated at 9:30pm 27 April to include most recent download and registration stats.