The three-day snap lockdown for Brisbane, starting this evening, comes on top of similar measures imposed in Sydney, Perth and Darwin in recent days.
These are tough decisions, Queensland state Premier Annastacia Palaszczuk said, after Australia recorded 23 virus cases in 24 hours.
Australia has been broadly successful in eliminating local transmission through a mix of border closures, mandatory hotel quarantine for overseas arrivals and snap lockdowns.
Less than five per cent of adults are believed to have received both vaccine doses.
As well as Brisbane, surrounding coastal regions and the small northern city of Townsville are also subject to the latest order, after an unvaccinated hospital worker spent up to 10 days travelling around Queensland while infectious.
This morning, Perth residents woke to a four-day snap lockdown after a local cluster grew to three cases.
The largest outbreak is in Sydney, where 150 people have tested positive for COVID-19 since mid-June, with the city’s residents now under stay-at-home orders for two weeks.
In all locked-down areas, people are generally required to stay at home except for essential work, exercise, to buy groceries or for medical reasons. Masks are mandatory across swathes of the country.
Australia has recorded a total of just over 30,000 cases and 910 deaths in a population of about 25 million since the pandemic began.