NSW and Victorian chief health officers have warned communities this week to remain vigilant as Omicron subvariants BQ.1 and XBB are tipped to become dominant variants throughout Australia.

In Singapore, it only took three weeks for XBB to overtake every other variant in the island country.

Because these new variants can more easily escape immunity from past infection and vaccination, health authorities have warned Australia is at the start of another COVID-19 wave.

In Victoria, hospitalisations increased by 20 per cent in the week leading up to October 28, prompting the Victorian CHO to encourage people to take appropriate mitigation steps such as vaccination and self-isolating when symptomatic.

There are currently no mandatory isolation rules in place in Australia.

Last summer, COVID-19 rates spiked sharply over Christmas as restrictions were loosened and thousands were hospitalised with the virus.

Victorian Health Association deputy CEO Juan Paolo Legaspi said the health care system is bracing for another spike over the holiday season this year.

"As much as we wish COVID-19 was behind us, it isn't. Our health system is now preparing for a COVID-19 wave in December when they would usually experience lower demand for emergency care and have staff on leave to spend time with their families," he said.

"It's going to be intense, especially due to the healthcare worker shortage that is happening right across the country, particularly in regional and rural areas."

Despite driving an increase in cases, the World Health Organisation says XBB and BQ.1 are not different enough from other Omicron lineages to warrant labelling them as new variants of concern.

The Victorian Department of Health said the ability of XBB and BQ.1 to escape immunity from past infection, combined with waning immunity from past vaccination, was driving rises in cases overseas.

Monash University epidemiologist Associate Professor James Trauer said people should not panic about this new variant.

"We do now have a large amount of immunity in the community that will protect us," he said.

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Monash University's Mr Trauer said optimising individual protection was important, particularly for elderly and vulnerable people, as we faced another period of increased transmission.

"If you're elderly, if you have medical conditions that would put you at high risk of severe outcomes, then you do need to make sure that you've had all of the doses of vaccine that you're eligible for," he said.

A consistent vaccine supply was being met with dwindling demand, with Australia binning 17.6 per cent of the national stockpile in September.

Of the 1100 deaths recorded in Victoria in the past three months, 49 per cent hadn't received booster doses, that provide significant protection against the Omicron strain.

According to the Department of Health, while 95.8 per cent of people over 16 in Australia have had two doses of a COVID-19 vaccine, just 72.2 per cent have had three.

The Victorian Health Association said Victoria's first 'Covid normal' winter was extremely challenging for hospitals, with code 1 'lights and sirens' ambulance call outs the second highest on record.

"If you're riding around in the middle of nowhere off-roading and you break your bones, spare a thought for the people who have to treat you in hospital," Mr Legaspi said.

"Those types of risk-taking behaviours do add extra pressure to the system, and this is going to be a very difficult season coming up for people working in the health care system."

A National Skills Commission report showed that registered nurses were by far the most in demand job in Australia, with 9,266 jobs vacant.

The report names burnout as a key factor for people leaving the health care industry in the last year.