Western Australia's intensive care units are at risk of being overwhelmed and more people will die from a significantly bigger Omicron outbreak if the McGowan government waits too long to re-open the state's border, independent modelling has found.
These are the findings calculated by George Milne, an expert in infectious diseases modelling and professor of computer science at the University of Western Australia.
Professor Milne's work has previously been used by state and federal health departments and the World Health Organization to help determine policies and vaccine rollouts.
His modelling, which has recently concluded and will be submitted for peer review, examined the likely health impact once the WA border does open.
It is based on Office of National Statistics data from the UK, as well as information from the South Australian and Queensland outbreaks, to set the parameters for WA.
The modelling calculated the number of cases, hospitalisations, ICU admissions and deaths each month from February 5, which Premier Mark McGowan originally set as the reopening date before cancelling it indefinitely.
Impact to get worse as time passes
Professor Milne said if the Premier waited beyond May to reopen, the impact would become increasingly unmanageable.
He calculated that if the border opened on June 5, there would be a total of 478 deaths, 360 ICU admissions, 3,603 hospital admissions, and more than 885,352 cases during the Omicron outbreak in WA.
Professor Milne said a March 5 opening would be his advice for the Premier, but added he was "only a mathematician".
The modelling shows a relatively small increase in numbers if the border opened in either March, April or May.
Over that three-month period, the total number of hospitalisations for the Omicron outbreak would increase from 2,932 to 3,203, ICU admissions from 293 to 320 and deaths 383 to 421 depending on which month the border re-opens.
"What we see is that if the border opens in March or April or May, we get quite a contained outbreak," Professor Milne said.
"And if we were to look at the end point of our modelling, which is ICU bed demand, fully-staffed ICU bed demand, that can be managed, the peak of the outbreak can be managed in terms of cases that end up in ICU, if the border opens up in the next few months.
"However, if the border opens from June onwards, the number of cases, people hospitalised and ending up in ICU steadily increases month by month to the point where ICU facilities may well be overwhelmed.
Professor Milne said the reason the Omicron impact grew each month was because vaccine immunity would start declining around the middle of the year before dropping rapidly, making the population more susceptible to the virus.
"If we leave opening the border too late, we'll get a higher peak of all these health burden metrics, which causes real concern in terms of hospitalisations," he said.
WA's Chief Health Officer Andy Robertson has also previously told the government that beyond March, waning immunity will start to become a problem, at the same time as the winter months and flu season approach.
"What's going on here is while vaccination is still being carried out, that's increasing the immunity profile in the overall WA population," Professor Milne said.
"Coming along behind that is immunity waning and if we leave it too long...the immunity profile of the population will drop significantly, resulting in a much bigger Omicron outbreak."
According to the modelling, if the border did not re-open until September, there would be 644 deaths overall, 478 ICU admissions, 4,782 hospital admissions and a total of 1,107,195 confirmed cases.
WA government waves off concerns
Health Minister Amber Jade-Sanderson dismissed Professor Milne's modelling.
"I have not seen that," she said.
"I think the reflection of the CHO is that Professor Milne has done, has assisted with some modelling in the past, but he is not an epidemiologist, he is a mathematician and we take advice from the public health officials who are epidemiologists."
Mr McGowan on Tuesday said he had not seen any Omicron modelling.
Ms Jade-Sanderson on Wednesday said she thought Chief health Officer Andy Robertson had examined Professor Milne's modelling.
"But there is a number of factors that are in place that determine that decision making, including the vaccination rates," she said.
"Children have not all been vaccinated yet, we still want many children to do that.
"A number have had their boosters, but to be fair to the people who are not even eligible for their boosters, we need to give them more time.
"And what we want to do is increase those vaccination rates across the community before we have a steep spike in Omicron."
