The territory's third lockdown extension five weeks into its outbreak follows concern about the continued number of cases infectious in the community.
Chief Minister Andrew Barr, whose Tuesday announcement was foreshadowed to be about steps towards reopening, confirmed the lockdown would continue until October 15.
This is because of the ongoing public health risk in Canberra, particularly the number of people still out and about while infectious.
The return of the Yass Valley Council in the New South Wales Southern Tablelands to lockdown has also factored into the ACT's decision.
Of Canberra's latest cases, taking active infections to 252, 14 could be linked and just two were in quarantine the whole time.
Mr Barr said the government had sought to pick "the least-worst option".
This includes a review of restrictions in two weeks' time.
Health officials have identified six separate incursions of the virus into ACT from NSW and two from Victoria.
The aim is get the number of people infectious in the community as close as possible to zero.
"It has not been a good day on that performance objective. We have had other days that have been considerably better," Mr Barr told reporters.
"We are all in this situation because of a failure in NSW. We all know that. That failure has spread into Victoria and the ACT.
"Ultimately, the desirable outcome is that there aren't internal state borders in Australia. I hope that happens by Christmas. It may not, but I hope it does."
Some restrictions will be tweaked from this weekend to soften the blow. This includes allowing additional outdoor recreation such as golf and tennis.
Year 12 students who have had priority vaccine access are slated to return to class for the start of term four.
Year 11 students are due to follow on October 18 while others will continue learning remotely for at least the first month of term four.
The reproductive rate of the virus is sitting around one. This effectively means each case will give the virus to one other person.
The source of about 50 cases remains unclear and around half of these have emerged in the last fortnight.
Chief Health Officer Kerryn Coleman said restrictions on movement were the only way to reduce community transmission until jab rates increased.
Canberra has passed the halfway mark in fully vaccinating residents aged 16 and older.
It's expected to hit 50 per cent double-dose for over-12s this week.
Dr Coleman did not want to risk reopening too early only for Canberra to have to go back into lockdown.
Federal Health Minister Greg Hunt said it was a "difficult day" for people in the ACT.
"I completely respect the decision of the ACT," he said.
