South Australia has posted a major decline in COVID-19 cases, with 2193 new infections or almost a third fewer than on Friday.

However the state has recorded a further three virus-related deaths.

Health officials say the latest fatalities were a woman in her 30s, another in her 80s and one in her 90s.

South Australia is currently managing 33,892 active cases.

There are 276 people with COVID-19 in hospital, 37 of them in intensive care and seven requiring a ventilator.

Of those hospitalised, 161 people are fully vaccinated, 44 are either unvaccinated or partially so and 71 have an unknown status.

Some 90.2 per cent of South Australians aged 12 or over are double vaccinated while more than 452,440 booster shots have been issued, more than 18,000 of them in the past 24 hours.

Premier Steven Marshall says the state may have reached the peak of its Omicron-fuelled outbreak.

There were 3023 new infections reported on Friday and 3777 on Thursday.

"These numbers do bob around a bit but this is very significantly under our (3569) seven-day average," he told journalists.

"I'm increasingly hopeful we have got on top of this very dangerous Omicron wave."

SA also confirmed six deaths on Friday and 298 hospitalisations.

Genome sampling indicates 95 per cent of its recent cases are the Omicron variant.

Mr Marshall says the latest preliminary modelling indicates there will be no significant jump in cases once school returns early next month.

Surveillance rapid antigen testing will be introduced for teachers and other staff in pre-schools and childcare centres.

The state's blanket work from home advice will also be revised on Thursday with workplaces asked to restrict attendance to 25 per cent of the usual capacity or about one person to every four square metres.

They will also be asked to wear masks indoors and take their lunch breaks outside where possible.

There will be no immediate change to other local restrictions.