Five South Australians with COVID-19 have died in the last reporting period, all of them in their 80s.
Hospitalisations have dropped to 285 people, including 24 in intensive care and four on ventilators.
The state has recorded 1,846 cases, the lowest daily numbers since the start of the year.
All but 3 per cent of the cases were the Omicron variant.
SA Health said those who died were four women in their 80s and one man in his 80s.
Density at hospitality venues will double to 50 per cent capacity from midnight.
Drinking while standing will still not be allowed indoors.
Elective surgery will be allowed for children.
Mr Marshall said restrictions on other sectors could come soon.
"We will be looking very carefully at some other sectors in the next round — certainly the fitness sector is one we are looking at," he said.
He said modelling did not predict a second wave of cases because of the eased restrictions and students returning to class.
Reduced requirement for QR code check-ins
QR code check-ins will no longer be required at retail venues.
Checking in using QR codes will still be required in hospitality venues and "high-risk settings" such as aged care and hospitals, the Premier said, along with gyms.
No venues have been publicly announced as exposure sites since January 6.
With masks required in retail venues, Mr Marshall said there had not been enough transmission for QR code check-ins to be worthwhile at shops.
However, he said they would still be useful in cases such as multiple positive infections occurring at a restaurant or a function.
"It's still useful to be able to send a message to people," he said.
The number of people checking in using QR codes has fallen substantially since Christmas, however, it is unclear if this is because of fewer people visiting businesses or people not complying with the rules.
MP says Premier preferred wave in January to March
Meanwhile, state Liberal MP Nick McBride has defended his comments made at a Wattle Range council meeting last week which referred to reasons behind the Premier's decision to open the state's borders on November 23.
The Border Watch newspaper reported the Member for MacKillop said Mr Marshall "wanted the problems in January… nothing like that in March", alluding to the date of the state election — March 19.
Mr McBride told ABC Radio Adelaide this morning his comments related to opening the border in time for Christmas, new years and to reunite families for a better year in 2022.
Opposition Leader Peter Malinauskas said South Australians deserved an explanation.
"I don't think any South Australian believes that politics should be playing a role in such a critical public policy question and now the government has to explain themselves when one of their own MPs is on the public record," he said.
Mr Marshall said it was "quite frankly preposterous" that the government would base its COVID-19 border restrictions on their effect on the election outcome.
"Our decision in South Australia was very clearly made in accordance with the national framework which was agreed in July last year," he said.
Of the 105 people with COVID-19 who have died in South Australia since the start of the pandemic, 101 of them have lost their lives since the state's borders opened to Victoria, NSW and the ACT on November 23.
Teachers agree to postpone strike
South Australian teachers have agreed to call off a strike planned for the first day of term.
It was to be held over concerns about the state's return-to-school plan.
On Monday, two-thirds of teachers who responded to a union ballot voted to take a day's stop-work action on the first day of school.
But the union held a second vote, which closed on Friday evening, following what it called constructive discussions with the government.
The second ballot resulted in 76 per cent of participating teachers voting to postpone strike action until further notice, "pending continued constructive negotiations with the Department for Education and the government".
The Australian Education Union SA president Andrew Gohl said the education department had committed to continuing discussions on issues such as safe working provisions for vulnerable workers and workers with vulnerable family members, as well as COVID leave.
"We understand that this dispute came at a difficult time for families," he said.
"However the advice from education professionals was to delay the start of the school year by two weeks.
"This would've given a reasonable opportunity for the AEU to work with DfE [Department for Education] collaboratively and carefully through the complex issues that Omicron presents for education.
"Instead the Premier failed to heed that advice, failed to listen, and members were left with no option but to take action to address the issues created by a muddled start to the school year."
