Melbourne could remain under stage-four restrictions until mid-October, according to modelling from Melbourne and New England universities, which suggests if restrictions are lifted before the 14-day average drops below 25 new cases a day there would be a third wave of infections.
The modelling was released by the Victorian government in the lead-up to a much-awaited press conference by the premier, Daniel Andrews, on Sunday which will set out the plan for moving the state out of lockdown.
Stage-four restrictions, which were introduced in Melbourne on 2 August, are due to expire on 13 September. Andrews has already hinted they may be extended.
A draft version of the roadmap, obtained by Guardian Australia on Saturday, suggested that stage four could be extended to 28 September, with the added provision that people who live alone could nominate one visitor to their home. At the moment, in-house visitors are only allowed if they are intimate partners.
The new modelling, circulated by the premier’s office, indicates that the restrictions could be extended until the daily case numbers average 25 new cases a day or lower – which, on the current rate of decline, would mean extending stage four for four to five more weeks.
It warns that if restrictions are lifted too early there will be a yo-yo effect, which would mean that Melbourne was lifted out of stage-four restrictions for a few weeks and then placed back under them in November or December.
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“In 640 out of 1,000 model simulations, reopening too early (at 25 cases per day over the fortnight, on average) causes a yo-yo effect,” the report on the modelling states.
Regional Victoria is under stage-three restrictions and was never placed under stage four.
The modelling report states that “less stringent stage three restrictions have proven ineffective in Victoria”. Under stage three even with compulsory face masks, it says, it took 49 days for the 14-day average of daily case numbers to halve. With stage-four restrictions in place for Melbourne the state’s daily case numbers were halving every 18 days.
“Keeping Stage-4 restrictions until case numbers are low enough to safely reopen will enable all Victorians to get back to Covid-normal, faster,” the report says. The modelling assumes 90% compliance with wearing face masks.
As of Friday, the 14-day average was 116 cases a day. By mid-September, the modelling shows, the 14-day average will be 63 cases a day. The report makes a point that New South Wales, in its second round of infections, has never had a 14-day average of more than 13 “domestic” cases a day.
“University of Melbourne modelling finds that it is unlikely we will have aggressively suppressed the virus by mid-September,” the report states. “If restrictions are eased while the virus is still circulating widely in the community, there is a real risk that infections will rebound – causing restrictions to be reimposed and last much longer.”
Prof Marylouise McLaws, an advisor to the World Health Organisation on Covid-19, said that the modelling was “conservative which is good,” but she would suggest stage four restrictions remain in place until the daily case numbers are in single digits.
“I would suggest that it’s still high – 25 cases in a day is still very high,” she told Guardian Australia.
But, McLaws said, the modelling was unable to distinguish between community transmission cases and those from known clusters, which would be easier to control. The government would account for that, and for compassionate issues like people struggling under lockdown, in formatting its roadmap, she said.
“If they lift the restrictions too soon I believe that behavioural factors will increase and you will have a spike again, and you don’t want that to happen. It will ruin all of the hard work.”
The epidemiologist said the government would have to allow for some easing of the rules, including potentially easing restrictions in regional areas with no active cases, to ensure continued community compliance. “Otherwise it will be very hard for the community to support the idea, they are suffering emotionally and economically and you have to factor that in,” McLaws said.
Jennifer Westacott, the chief executive of the Business Council of Australia, said she was “really worried” by suggestions Victoria’s lockdown would be extended.
“That means more job losses, more business failures,” she told ABC’s Insiders on Sunday. “It means businesses leaving Victoria. It means a sense of hopelessness that I think has crept in to Victoria, which I think is bad for people’s mental health.”
Westacott, who is also a director of Wesfarmers, questioned why large retailers such as Bunnings, Target, Kmart, Big W and Officeworks may not be allowed to reopen even if they have Covid-safe plans and there is no evidence of “customer transmissions”. Regions with no new cases should also be allowed to reopen, she argued.
The business council boss acknowledged the Victorian government had consulted business ahead of the announcement but said the process was not “good enough”. Westacott suggested employers had advance notice of the roadmap but the government had not worked with them to “to try to make sure that we don’t get a third wave and that we keep things going”.
The leaked draft roadmap suggested stage four would be extended before easing into a stage-three phase which would be more restrictive than the previous stage three. A requirement to “stay local” would remain in place and exercise limits would continue although be increased to two hours a day. Only essential retail businesses would be allowed to open.
It says stage three-restrictions could remain in place until there were fewer than five cases a day on average, with less than three of them from an unknown source.