The ACT recorded 12 new cases of COVID in the 24 hours to 8pm Wednesday.
Six of the new cases are linked to known cases, while six remain under investigation.
ACT Chief Minister Andrew Barr said four of the new cases were in quarantine for all their infectious period, and eight were in the community for part of their infectious period.
He warned of challenging scenarios ahead for the territory, with no easy choices, but said he was still aiming for no active cases in this outbreak.
There are now 13 people in hospital with COVID. Four of those are in intensive care and two are on ventilators, up from one on Wednesday.
The new case who is on a ventilator is a man in his 20s, who has no underlying health conditions and was unvaccinated.
Of the cases in hospital, the youngest is just 18 and the oldest is 54.
On Wednesday, 2500 tests were conducted at clinics across the ACT, well down on the 3763 recorded on Tuedsay.
Mr Barr said that figure was not high enough, particularly with the virus spreading in the community.
There are now 309 cases associated with the latest outbreak. However, 51 of those cases have now recovered, leaving 258 active cases.
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Meanwhile, two new COVID cases have also been recorded in Queanbeyan.
The Queanbeyan cases have been linked to the Canberra outbreak, and there have been no exposure sites listed. ACT health authorities are investigating them.
ACT deputy chief health officer Dr Vanessa Johnston said 1100 people had self-identified as a close contact and a further 4200 were casual contacts.
There are now 220 current exposure sites, and 12 major clusters in the ACT:
Dr Johnston said there were now 20 cases associated with Canberra's disability community, an increase of two.
Mr Barr said Canberra's 75-79 year olds became the first cohort in the country to get to 80 per cent fully vaccinated.
There were 16,210 people between 16 and 29 years old who made a vaccine booking on Wednesday, when Pfizer doses were made available to that age group.
The mass vaccination centre at the AIS Arena will begin operations from 10am Friday.
The Chief Minister said there would be challenging scenarios ahead.
"There are no easy choices," Mr Barr said.
"The next few months while we fully vaccinate hundreds of thousands of Canberrans are going to be difficult.
"Canberrans have worked had to minimise the spread of the virus and reduce risk to the community.
"Vaccines will do most of the heavy lifting."
While Victoria and NSW authorities have conceded that getting case numbers back to COVID zero may not be possible, Mr Barr said it was still possible in the ACT.
"It's not out of reach in relation to this outbreak," he said.,
"The [reproduction rate] is well below one, and if we continue on this trajectory we would be able to contain the outbreak and get to a point where there is no infectious cases in the community.
"But I readily acknowledge that we are still at extreme risk from NSW."
The ACT's reproduction rate is 0.8, meaning one person will spread the virus to an average of 0.8 people.
Dr Johnston said while there had been days throughout the lockdown of higher case numbers, the rolling average of cases was steadily going down.
"Because of the tough restrictions, and they are challenging, it's why we're not seeing rapidly escalating numbers," she said.
"If we were out and about as normal, given the current levels of vaccines, those numbers would be skyrocketing."
Health Minister Rachel Stephen-Smith said there were now fewer than 300 ACT Health staff in quarantine or isolating. More than 200 additional health staff, mainly retired or student nurses, have been brought on board.
Ms Stephen-Smith said at least 60 per cent of health staff in the ACT had been vaccinated, based off data from a self-reported survey of health workers, but vaccination rates were estimated to be higher.
In the past day, police conducted 110 traffic stops and only issued one direction to leave the ACT.
The new virus figures come as the ACT gets set to enter its fourth week of lockdown.
The lockdown was initially set to end on September 2, but a decision was made to extend the restrictions earlier this week until September 17, due to a rising number of cases and people being infectious in the community.
From 5pm on Thursday, some restrictions will be eased, including people being able to spend a maximum of two hours outdoors with people from their household, or up to five people.
Playgrounds will be able to reopen. Outdoor businesses such as gardeners, landscapers and pet grooming are also able to recommence work under strict COVID protocols.
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