Acting Premier James Merlino outlined the steps on Thursday as the state recorded another 2000 cases and case numbers exploded in NSW to almost 6000 in a day, as fears over the Omicron variant continue to grow.

"With the emergence of Omicron and significant numbers, particularly in New South Wales and Victoria, the Minister for Health on advice of the Chief Health Officer has recommended additional measures to slow the spread and to keep Victoria open," Mr Merlino said.

"So what that means, from 11:59pm tonight, the following additional measures will apply in Victoria: face masks will be required in all indoor settings, except private homes, for persons eight and over."

Face masks will also be required at all major events over 30,000 people, outdoors when moving around, although masks can be removed when seated outdoors, he said.

Mr Merlino said the practical steps were limited but were only possible because of the vaccination coverage that had been achieved so far.

"Ultimately, we're able to keep our state open because more than 90% of Victorians got vaccinated and we're vaccinating our way through this variant as well," he said

"My final message is if you are eligible for your third dose, make a booking and get it done. If are not yet double dosed, make sure you get your second dose and if you haven't got your first one, please get it done.

The government has also recommended people work from home across the festive season.

Chief Health Officer Brett Sutton defended the new mandate and said weak half measures of simply suggesting people wear masks would not be decisive enough to halt the contagion.

"So, the difference between highly recommending something and mandating something is the level of compliance that we see," he said.

"I have just pointed out to you the masks that we saw come off as soon as we went from mandate to strongly recommended. We usually get about 50% levels of cooperation or compliance with a strong recommendation. It goes to 95 - 99% with a mandate. Why would you introduce a half measure when you need the full measure to be in place?

Professor Sutton would not be drawn on the weakness of the Prime Minister simply recommending masks but said the value in the mandate was in the overall and rapid social change in behaviour to halt Omicron.

"A mandate is something that all the chief health officers were clear on," Professor Sutton said.

"They know know what a mandate means in terms of introducing an immediate social norm, a social position, if you like, and we see people responding to that. That is not to say that there is not personal responsibility in this space, but that there is a collective response ability and a mandate affects that."

Professor Brett Sutton said the Omicron variant might be a fifth as severe but figures from NSW show it was 15 times as contagious and the best tool to combat people, particulalrly the vulnerable was the booster.

"The difference is who is eligible to get it right now as we face large numbers of Omicron and having those individuals eligible and perceiving that booster will protect them," Professor Sutton said.

"We need as many people in that category already boosted as we possibly can, especially those at risk of dying."

Mr Merlino also urged people to come forward for the third dose.

"Boosters give a connotation of it being an optional thing that's nice to have. It is not, " Mr Merlino said. "The third dose is critical in our fight against this new variant and we've got this window of opportunity. We're seeing what's happening in the Northern Hemisphere in the colder months through this summer period, getting the third dose is so critical to combatting and we've got to take up that opportunities.

Victoria has reported 2005 new COVID-19 cases and 10 deaths.

Thursday's daily case figure is the highest in Victoria since October 22 when the state recorded 2160 cases, and has pushed up active infections to 14,801.

A total of 398 patients are in hospital, including 72 who are actively infected with the virus and in intensive care, with 39 on ventilators.

The seven-day hospitalisation average is steady at 391.

Testers processed 85,112 results on Wednesday, while 16,758 people were vaccinated in state-run hubs.

Australia's Chief Medical Officer Paul Kelly "highly recommended" wearing masks indoors and other places where social distancing is difficult at Wednesday's national cabinet meeting, but did not call for blanket mandates.

The Victorian government had flagged it would relax mask requirements last week but instead kept mandates in retail settings, for hospitality workers and on public transport, citing the spread of the Omicron variant.

Meanwhile, Victoria's testing system continues to strain under the weight of holidaymakers seeking a swab for interstate travel, with at least 20 sites across Melbourne temporarily closed as of 9am after reaching capacity.

Mr Weimar said more than a quarter of total tests in recent days had come from people needing a negative result to journey to Queensland, South Australia, Tasmania and the Northern Territory.

He blamed the long queues and waiting times on the "bureaucratic" requirement, and hopes other jurisdictions will move to a "more sensible arrangement".

The Australian Health Protection Principal Committee will report back to states and territories on whether PCR tests should be required for interstate travel, or can be replaced by rapid antigen tests.

Australian Associated Press

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