A record number of coronavirus tests in the past 24 hours revealed four new locally-acquired cases overnight, including one believed to be the state's first community transmission "in months".

All the locally acquired cases are linked to the current outbreak, which now has 15,000 close contacts.

The linked locations are state-wide, including in Bendigo and Cohuna.

However, Professor Sutton said there may be scope to "carve out" parts of regional Victoria without cases to be exempt from the remainder of lockdown.

"I understand the reflections of regional Victorians who are rightly saying they have not had cases for many months and for some local government areas, for over a year," Professor Sutton said.

"The reality is if we carved out a part of regional Victoria and said no restrictions in that place, that's where everyone from Melbourne would go and that would introduce this virus into previously unaffected areas.

"There are operational considerations about how you stop some of the potential movement if you were to carve out one area or many areas of regional Victoria.

"That said, these restrictions are under review and reconsideration every single day and if there is an operational response that can manage that and carve out parts or all of regional Victoria or, indeed, parts of metro Melbourne, that will always be under consideration but what we do not want to do is export this virus to previously unaffected areas."

He said the lifting of restrictions wasn't necessarily dependent on zero new cases.

"There is no single figure threshold for how you respond," Professor Sutton said.

"The considerations relate to new exposure sites and the number of new cases but also how many contacts they have, how many places they have been to and the kind of risk settings and the relative seriousness in those settings that have to be under consideration."

There were 17,223 vaccine doses administered yesterday and 47,462 test results received.

"It's the highest number of tests that we have ever done in Victoria," the Chief Health Officer said.

The state government has requested 160 Australian Defence Force staff from the Commonwealth for at least the next fortnight to assist Victoria with the latest outbreak.

State testing lead Jeroen Weimar urged all eligible Victorians to get vaccinated and to be patient with the state's cumbersome phone booking service.

"We have a decent supply (of AstraZeneca and Pfizer vaccines) at this point in time to do at least double the numbers we have been doing every week," he said.

"Over the past few weeks we have an average of 50,000 doses per week.

"We can double that number and we are on track to do that with the numbers we are seeing over the last few days."

Victoria is getting getting 71,000 doses of Pfizer per week and a "significant" increase in the allocation of the AstraZeneca vaccine.

The question playing on many people's minds is: will this just be seven days, or will it be longer?

In short, it's too early to make that call, Professor Sutton said.

"It is still the case that we are very, very early in this," he said. "We have to see how the days ahead play out.

"Community transmission is still expected to occur; we just need everyone who has been contacted to absolutely abide by the quarantine regulations that will be in force for them as primary close contacts and their secondary close contacts.

"They are the most important cohort to stay hunkered down, to get that test, and to remain in strict quarantine for the 14 days."

Contact tracers know there's a link to the man who came from hotel quarantine in South Australia.

Professor Sutton said there's a potential he was out in the community for 12 days before he got tested.

"We are encouraging absolutely everyone at the first sign or symptom of illness, and it can be very mild - it can be just a tickle in the throat or just a runny nose or just a headache or lethargy.

"Do not think that it is something else. You have to work on the assumption that it is COVID.

"Get that negative test, and then assure yourself you are not putting others at risk.

"We can't emphasise it enough. It is out there in the community, you have to assume it is COVID until proven otherwise."

There were a record 17,223 Victorians vaccinated in the past 24 hours.

If we continue at this rate, the state will be fully vaccinated by the end of 2021, Professor Sutton said.

"If we continue at 17,000 through our state vaccination sites, and similar numbers through our GPs, we will be on track to be completed by the end of the year," he said.

"We know that as AstraZeneca's second dose kicks in that the numbers need to ramp up again, so you've got those coming through now to be vaccinated as well as those who need follow-up dose for Pfizer or AstraZeneca.

"There will be an increase in numbers in coming weeks just by virtue of the second dose requirements coming through.

"I hope we are on track for the end of the year. We can do it."

Infectious diseases expert Professor Professor Ben Cowie said vaccines were crucial to preventing further lockdowns in the future.

"These vaccines are game-changers, they are saving and have already saved hundreds of thousands of lives overseas," he said.

"They are, right now, getting Victoria into the place where we are saving lives with our vaccines today.

"We need to get as many Victorians who choose to be vaccinated, vaccinated as quickly as we can

"These vaccines, the AstraZeneca and Pfizer, are hugely effective at preventing serious illness, preventing hospitalisation, and preventing death.

"The real-world data coming out of Europe shows us that these are our way out of this situation, and they will protect our health system and protect the lives of Victorians as we do so."

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