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Hospitalisations for COVID-19 Omicron cases are running below projections in South Australia but still have the potential to become "a very large number", Premier Steven Marshall says.
With 3493 new infections reported on Wednesday, SA has 125 people in hospital - a rise from 102 the previous day.
The number in intensive care has remained unchanged at 12, with one person on a ventilator.
Mr Marshall said those statistics are being fed into the latest modelling, which is being revised significantly since Omicron took over from Delta as the dominant variant.
"The pleasing thing is, with Delta we thought there would be about five per cent of people that would end up in hospital," he said.
"We've been working on around one per cent in terms of Omicron but the data in South Australia would suggest it's closer to 0.5 per cent.
"So there is some upside, but the problem is 0.5 per cent of a very large number is still a very large number."
Mr Marshall also signalled an intention within the next week for SA to switch to rapid antigen tests (RATs) for close contacts of virus cases, to preserve the more conclusive PCR tests for people with symptoms.
The RATs for close contacts will be free.
The change comes as demand remains high for tests with more than 21,000 performed on Tuesday.
"As we get further towards the peak we want to preserve that PCR capacity for those people who have symptoms so they can get through in a rapid rate," the premier said.
"At the moment I think we still have the highest per capita PCR testing in the country and the lowest turnaround times.
"But we've got to be mindful of where we're going to be in a week's time, in two weeks' time, in three weeks' time."
With only a modest rise in case numbers on Wednesday, Mr Marshall said SA was doing better in restricting the spread of the virus.
"If we look at that doubling rate in South Australia, it's around four or five days, very different from some other states at the moment," he said.
"We'd like to push that our further because we just don't want all of those new infections hitting all at exactly the same time."
However, the premier said the peak for case numbers was still weeks away and infections would persist at high levels for some time after that before starting to fall.
SA currently has 19,250 active infections with 400 cases reported across the state's aged care sector.
SA Health said about 200 of those were among staff and 200 among residents, with more than 100 facilities reporting infections so far.
There have also been about 270 cases among the state's broader health workforce.
The Ambulance Employees Association said more than a dozen ambulances were left unstaffed on Wednesday because of a shortage of available paramedics.