The delay in reopening Western Australia to the rest of the country will achieve very little in the way of public health, according to a WA infectious disease modeller.
University of Western Australia professor George Milne has prepared new modelling on the Omicron variant, and had in the past advised WA Health on the COVID-19 pandemic.
He said the build-up of immunity from booster doses — which the state government said it wanted to increase before reopening — would be countered by waning immunity from those who have already had the vaccine.
"And there's a point where it doesn't make much difference if we delay opening borders very much," Professor Milne, from the Department of Physics, Maths and Computing, told ABC Radio Perth.
He said his modelling — which looked at the curves in other states and in the UK — took into account an influx of cases when the borders opened.
"We find that we get quite a stable situation with the level of immunity in the population," Professor Milne said.
Boosters needed for reopening: Premier
When Premier Mark McGowan announced last week the border opening was being delayed indefinitely, he said it would be irresponsible to open as planned on February 5 because there was science showing the state needed to increase its booster doses.
The WA government has not released its modelling on the Omicron variant despite calls from the opposition to do so.
Chief Health Officer Andy Robertson told ABC Radio Perth on Thursday the government had "preliminary" modelling on Omicron.
"It looked at what the picture might be and it was not dissimilar to what we've seen in other states," he said.
But Dr Robertson said the decision to delay the border opening also took into account there were already some cases of COVID-19 in the community.
He reiterated the importance of booster doses, saying they would help reduce hospitalisations and serious disease.
"So if we could get our population boosted up over the next three to four weeks, noting that we still might have a homegrown outbreak occurring, that would [put] us in the best position," he said.
Health advice released in the lead-up to the border decision showed the government was expecting 75 per cent of the eligible population to get a booster shot by March 2.
Hospitals can 'easily' handle infections: CHO
Dr Robertson said the state's health system would be able to deal with hospitalisations at the rate that South Australia was currently experiencing.
There were 285 people in hospital in SA on Friday, including 24 in intensive care and four on ventilators.
"We could easily deal with that", Dr Robertson said.
He also said West Australians would face further restrictions as numbers increase.
"The government still needs to make a decision on where we end up in this space and that's obviously something that is sitting with government at the moment," Dr Robertson said.
Shorter but sharper Omicron peak predicted
Mr Milne's modelling suggested while the Omicron cases would be much higher than those of Delta, the peak would be much shorter lived.
His data showed the Omicron peak would arrive about 50 days after the borders reopened, and would last about two weeks.
It predicted demand for WA hospital beds from Omicron cases would peak at about 430 beds.
He expected about 10 per cent of those beds, or about 43 people, would be in intensive care.
That was compared to about 54 general ward beds and eight in intensive care under the WA Health modelling for the Delta variant, with vaccine rates at 90 per cent double-dose.
"It seems to grow rapidly and decrease rapidly," he said.
Mr Milne was optimistic about the WA health system's capacity to handle the arrival of Omicron.
"The interesting thing with Omicron is it seems to be much sharper and you get a lot of cases coming on quickly and then they decline quickly," he said.
"Whereas Delta, it grew more slowly … and stayed high for a while and took quite a while to decline."
A statement from WA Health said it had enough capacity to surge to 316 ICU beds when needed.
"At the system level, WA Health has done extensive planning in areas including personal protective equipment, hospital capacity and patient flow, testing, workforce planning, infrastructure, and managing COVID-19 in the community," it said.
Editor's note (March 1, 2022): This story has been corrected to make clear that Professor George Milne is an infectious disease modeller from the University of Western Australia's Department of Physics, Maths and Computing.
