The BA.4 and BA.5 subvariants now make up more than half of the COVID-19 infections recorded in South Australia, which is resulting in a surge of cases that is close to peaking.
Chief Public Health Officer Nicola Spurrier said just under 55 per cent of genomic samples of COVID-19 infections taken last week were of the newer versions of the Omicron variant, up from about a quarter the week before.
"We've seen a doubling," Professor Spurrier said.
"I don't even think we had one sample of BA.1 in that last week's run.
"We've still got BA.2 around but you're seeing more of BA.4 [or] BA.5."
SA Health predicts hospitals will have an increase of COVID-related patients in three weeks' time after a peak of new cases in three days.
The state recorded 4,408 new COVID-19 cases today, the most new cases in one day since the middle of May.
It brings the state to 24,166 active cases.
Two people with COVID-19 have died – a woman in her 60s and a man in his 90s.
A total of 245 people with COVID-19 are in hospital, including six people in intensive care.
Reinfections more likely but no mask mandate
The period of time which a COVID-positive person is considered immune after infection has changed from 12 weeks to 28 days because people are more likely to catch the BA.4 or BA.5 subvariants even if they have previously had a coronavirus infection.
Professor Spurrier said more reinfections were expected.
"If you've had an infection, after 28 days and you get start to get symptoms, you need to get retested.
"It's important you isolate away from others."
She said mask mandates would not come into effect unless the state was moved back into a state of emergency.
"We would either have to call a public health emergency or a state emergency and I don't think we are at that stage at the moment," she said.
"But of course we will continue to monitor the situation.
"We have a lot of people reinfected wandering around in the community infecting people.
"It's really important in the three or four week period we try to be protected as we possibly can."
New vaccination hub in parklands
A new vaccination clinic opened today in the Adelaide Parklands, in Ellis Park, off Sir Donald Bradman Drive, ahead of the nearby Adelaide Showground clinic closing tomorrow, ahead of the Royal Adelaide Show.
The Pfizer vaccine will be available at the clinic for anyone over the age of five.
People aged 30 or over will be able to get a fourth vaccine dose.
The Myer Centre clinic at Rundle Mall will reopen on Friday, while the Enfield clinic is set to return later this month.
Health Minister Chris Picton said the new hubs would help meet demand as people opted for a fourth dose.
He urged South Australians to roll up their sleeves.
"On Monday, the first day of the vaccination program, there was 6,600 South Australians who rolled up their sleeve to get vaccinated," he said.
"Seventy-five per cent of those people did it at GPs and pharmacies across the state.
"One part of the parklands we have the vaccination hub, the other side we have PCR testing and another part of the parklands we have the rapid antigen tests."
The Victoria Park testing clinic closed on July 1 ahead of the Adelaide 500 returning to the area in December.
Deputy Premier Susan Close said the state government would not be offering free RAT kits for concession holders, after the federal government confirmed its program to offer up to five per month would end on July 31.
"There's no plans I've seen to suddenly purchase RATs regardless of whether you're a close contact," Dr Close said.
"We've established a requirement to make sure people can do that without a cost to themselves."
