The ageing Australian Institute of Sport Arena has been transformed into a mass vaccination clinic, where thousands of Canberrans are expected to receive their jabs.

The ACT government is confident the increased capacity at the Arena clinic - which can administer 24,000 vaccine doses a week - will mean the territory consistently has more capacity to administer vaccines than supply.

Appointments for the Pfizer vaccine opened to Canberrans aged 16 to 29 on Tuesday, with strong demand pushing booked slots out to November.

Chief Minister Andrew Barr on Wednesday said it was difficult to say how long the AIS Arena vaccination clinic would be in place.

"As long as people want to keep getting vaccinated, we want to keep on vaccinating people," he said.

About 6500 new bookings were made in the first four hours that appointments were available to 16- to 29-year-olds.

By 5pm, 14,617 bookings were made for first-dose vaccinations, with ACT Health handling 3353 phone calls. There were just over 3000 call backs left to be made.

The booking system temporarily crashed on Wednesday morning, after people who had registered in advance were notified appointments had been made available to them.

Mr Barr acknowledged the high demand and the long wait time for an appointment.

"So, as always, the AstraZeneca vaccine is more readily available now through GPs and pharmacies. Being vaccinated is the best way you can avoid serious illness and hospitalisation," he said.

Mr Barr confirmed the ACT government had a commercial arrangement with the federal government to use the arena as a vaccination hub.

The AIS Arena was effectively mothballed last year, after potentially serious fire risks were identified in the four-decade-old venue.

The ACT government has previously ruled out buying what is the territory's largest indoor venue, but has encouraged the federal government to commit to minor upgrades to keep the facility running while the territory builds its own indoor venue.

A final decision on the facility's future had not been made, federal Sports Minister Richard Colbeck said in February.

Health Minister Rachel Stephen-Smith, speaking last month, said safety concerns at the AIS Arena would be addressed before it reopened as a vaccine clinic.

"This is a very different use of that space, it doesn't require lighting around the arena that would be required for a big sporting event," Ms Stephen-Smith said.

"Of course, you don't have the crowds all in one place at one time, you have people moving through the venue in much smaller numbers than you would for a big event."

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The opening of the AIS Arena clinic will allow the Garran surge centre to be used for Covid testing, while also allowing the site to be on standby as an overflow COVID-19 ward should the ACT outbreak worsen.

Meanwhile, more than 87 per cent of residential aged care staff in the ACT have had at least one dose of a COVID-19 vaccine, while 54.3 per cent have had both doses.

Ms Stephen-Smith said the first dose vaccination rate had been doubled in the space of three weeks, ahead of a vaccine mandate.

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