What to expect from Australia's fifth wave of the Omicron strain

Deakin University chair in epidemiology Professor Catherine Bennett warned Australians should prepare for a "winter climb" in case numbers.

In the past seven days, 38,226 COVID-19 cases were reported around the country, which is an increase of almost 20 per cent on case numbers from the previous week.

"We're seeing numbers push up again which is what you expect as you get into colder weather," Professor Bennett said.

A rise in deaths from respiratory conditions during winter is expected, she said.

Immune systems are often not functioning as well as they do in mid-summer and winter brought more virus exposure, Professor Bennett said.

"It's the time where everybody just needs to be that bit more mindful of respiratory infections."

Immunisation Coalition CEO Kim Sampson said COVID-19 wasn't "behaving in a seasonal way like influenza".

"But maybe that's about to change. This year we could see COVID-19 sit more firmly in the seasonal cycle," Mr Sampson said.

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Most Australians have had at least one infection and vaccination, Professor Bennett said.

"We're in a situation where, for middle aged and older adults, we're seeing less cases translate to hospitalisation," she said.

Australia has "less deaths per infection than we have seen before", attributed to broader COVID-19 immunity in the population, Professor Bennett said.

"Our hybrid immunity does help protect us but it shouldn't take away from public health advice," she said.

Professor Bennett advised that winter was a good time to book in for a booster, particularly for those aged over 65.

Meanwhile, Mr Sampson said Australia had shown a "decline in interest" for COVID-19 boosters.

"We're still not getting the level of vaccination that is ideal to combat a disease like COVID-19," he said.

The public health messaging that declared the pandemic was over was "unfortunate".

"While the pandemic may be over the disease isn't," Mr Sampson said.