SA reported 1147 COVID-19 cases on Monday, below the state's seven-day average of 1372, along with five more deaths.
There are 224 people in hospital including 16 in intensive care where five people are on ventilators.
The state's active infections have dropped to 14,635.
The fall in infections came after the release of new modelling which showed the easing of restrictions across SA would result in a rise in cases, but that should not amount to a second wave.
Yet the modelling, prepared by the University of Adelaide and released by SA Health, said a "larger exponential increase" could not be ruled out.
It forecast increases ranging from 10 to 13 per cent at each stage of lifting restrictions, including density limits across the hospitality sector.
The next changes are scheduled for February 15 with others planned for February 29 and March 15.
It also predicted a six per cent rise with the full return to school on February 14.
"Overall, it is estimated that this policy should not result in a second wave of cases," the modellers said in a briefing note.
"In that case numbers should mostly continue to decrease, although at a much slower rate than if activity restrictions were to remain in place."
Premier Steven Marshall said the government would receive an update on the modelling later this week but the continued fall in daily cases was further evidence the government's strategy was working.
"We've taken a prudent approach to lifting those restrictions. We haven't just ripped off the bandaid," he said.
Mr Marshall said the number of outbreaks among the state's Indigenous communities had fallen from nine to six while 24 Aboriginal people were in hospital including one in intensive care.
Among SA Health staff, those off work with the virus had fallen to 203, with another 104 in isolation as close contacts, while about 100 students and 100 teachers were among the existing active cases.
Also on Monday, a parliamentary committee was told health officials were worried that some COVID-19 cases were going undetected in the community.
"No jurisdiction in the world is fully confident of all the numbers that are out there, that's just a fact," SA Health chief executive Chris McGowan said.
He said part of the problem was the perception that Omicron was not a serious variant of the virus and people were not rushing to get tested.
