More than 12,000 people are in quarantine in the ACT, with 10,500 of those identified as close contacts of the 67 confirmed COVID-19 positive cases.

Thousands more have identified as casual and secondary contacts, placing pressure on food delivery services and testing facilities.

Mr Barr revealed on Monday that about 6 per cent of the ACT's population has had a Covid test since last Thursday. More than 8400 tests were conducted on Tuesday, which was another record day.

ACT chief health officer Dr Kerryn Coleman confirmed the median age of those infected was 19.5 years. The youngest person infected was a three-year-old.

The ACT recorded 22 new cases on Wednesday. All of the new cases had known sources.

Four of Canberra's cases remain unlinked.

NSW recorded 633 cases on Wednesday, with numbers expected to continue climbing. Mr Barr said easing restrictions for some industries, such as construction, would be inappropriate at this time.

The number of close and casual exposure sites in Canberra has reached more than 200, with an additional eight close contact sites identified on Wednesday night including Subway in Dickson, Iskia Athletic Club in Campbell and The Bucket Warehouse in Mitchell.

More schools have also been caught up in the territory's Covid outbreak with a further three schools listed as exposure sites. These were: Lake Ginninderra College, Harrison School and St Thomas Aquinas Primary School.

It has prompted the Independent Education Union of Australia to call on the ACT government to provide priority vaccinations for staff in schools and early childhood centres.

Lyneham High School has emerged as the site with the most transmission so far, with 15 cases linked to the school. There have been 13 cases linked to Fiction nightclub.

There were no further cases linked to the Greenway Views retirement village, Dr Coleman said all resident and staff on site had returned negative results.

However, the facility will remain locked down for two weeks.

READ MORE COVID-19 NEWS:

Dr Coleman said Canberra's cases were predominantly in young people.

"The median age is 19.5 years, which gives us an indication that half of the number of cases that we have is under 20 years of age," she said.

"The ages range between three years and 62 years."

Fewer than 10 per cent of those in ACT aged between 20 to 24 years are fully vaccinated, and only 3.7 per cent of 16 to 19-year-olds are fully vaccinated.

Dr Coleman encouraged younger people to speak to their GPs about vaccinations.

"We are in a situation now where we do have exposure to Covid potentially in the community, while we're trying to limit that [it] is a risk factor," she said.

"So I would encourage anyone to consider vaccination at this point in time and please go and have those conversations with your healthcare provider."

ACT Health Minister Rachel Stephen-Smith said GPs and pharmacies had reported increased demand from younger people for the AstraZeneca vaccine.

"I'm advised that ACT pharmacies would have done about 700 AstraZeneca vaccinations [on Tuesday]," Ms Stephen-Smith said.

Our coverage of the health and safety aspects of this outbreak of COVID-19 in the ACT and the lockdown is free for anyone to access. However, we depend on subscription revenue to support our journalism. If you are able, please subscribe here. If you are already a subscriber, thank you for your support. You can also sign up for our newsletters for regular updates.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: