The Melbourne-based Doherty Institute said the country's focus must shift to limiting the number of COVID-19 deaths and hospitalisations, from its current zero-cases strategy, when at least 70% of the country's population above age 16 is fully vaccinated.

"This level of vaccination will make it easier to live with the virus, as we do with other viruses such as the flu," it said in a statement late on Monday. "Once we reach 70% vaccine coverage, opening up at tens or hundreds of cases nationally per day is possible." Currently, 30% of Australia's adult population has been fully vaccinated while 53% have had at least one dose.

Australia in July unveiled a four-stage plan  back to greater freedoms with higher vaccination rates. But Queensland and Western Australia states flagged they may not stick with the agreement as it was framed when case numbers in Sydney were much lower.

Prime Minister Scott Morrison acknowledged the concerns of some states from the Sydney outbreak but said "forever" lockdowns will do more harm than good to the country. "It doesn't matter whether it's 30 cases or 800 cases, the conclusions are the same, and that's what the Doherty Institute said ... we can do this safely and we do need to do it," Morrison told Nine News on Tuesday.

Australia has suffered less from the coronavirus pandemic than many other developed countries with about 44,600 cases and 984 deaths. But a third wave of infections from the Delta variant has plunged Sydney and Melbourne, its largest cities, and capital Canberra in a weeks-long lockdown. Victoria state reported 50 new locally acquired cases on Tuesday, down from 71 a day earlier. Of the new cases, 39 have been infectious in the community, a number officials have said must return to near zero to ease curbs.