Health minister Greg Hunt hailed take-up since the app was released Sunday evening as "extraordinary", adding that 1.1 million people had downloaded the program by Monday morning.
In response to privacy concerns, Mr O'Brien said he was confident the app was another necessary step in Australia's fight against the virus. Many people have voiced concerns of an erosion of privacy, and potential misuse of citizen data by the government.
From teams of "corona detectives", to Army cadets making thousands of calls a day, here are some of the ways countries are tracing the spread of Covid-19.
Using a phone's Bluetooth, the app is created to identify users who spend more than 15 minutes within 1.5 metres of each other. The data will be stored in Australia, and the health minister said "not even a court order" would allow other authorities such as the police to access it.
The government hopes a broader testing regime and the contact tracing app will lead to a relaxation of social and trading restrictions imposed since the pandemic began, earlier rather than later.
Simon McGarr, director of Digital Compliance Europe said that the HSE needs to be more open about how the app will work and its data protection implications to gain public trust in it.
'No other government agency can use this information, no one in the commonwealth government at all, and in state authorities, only the health officer can use it, ' he said.
Canada, US extend border restrictions for another 30 days
USA goods and services trade with Canada totalled an estimated 718.5 billion dollars in 2018, according to US trade authorities. Some $2.4 billion worth of goods and more than 400,000 people crossed the border each day on average prior to the pandemic.
The app assists in the early alert and finding of people who may have been in contact with a person who has tested positive to coronavirus.
Despite the relative straightforwardness of how the app should work, some issues still remain.
New research from the Australia Institute shows that 45 per cent of Australians say they will download and use the mobile app, while 28 per cent say they won't.
'All of us have numerous apps on our phones which collect more data than we have here'.
The government has pledged to protect the COVID contact tracking app from "function creep" where information gathered starts being used for other purposes, such as law enforcement.
Launching the app on Sunday, Prime Minister Scott Morrison said it came on the advice of the Chief Medical Officer and would help save lives and livelihoods.
A few countries, including South Korea and Israel, are using high-tech methods of contact tracing which involves tracking peoples' location via phone networks, though such centralized, surveillance-based approaches are viewed as invasive and unacceptable in many countries.
"You wouldn't want to be capturing every brief contact", he said.