‘Highly theoretical’ modelling released yesterday describes the disaster of Australia doing nothing about the coronavirus pandemic
The government has released two modelling studies after weeks of clamour, but warned that they were highly theoretical, were not based on Australian data, did not take into account Australian mitigation measures, and could not be used to predict our COVID-19 course.
The Peter Doherty Institute for Infection and Immunity has worked with the government previously on pandemic influenza modelling, which was repurposed for COVID-19 and informed our early containment measures such as travel bans.
One paper led by Professor Jodie McVernon, director of Doherty Epidemiology, models what would happen to ICU capacity in the scenario that the whole country was infected.
Without mitigation measures, that “highly artificial and very unlikely” would result in 35,000 ICU presentations a day – a “horrendous scenario” beyond any health system’s capacity, in the words of Chief Medical Officer Brendan Murphy yesterday.
Quarantine and isolation measures would blunt that peak somewhat, but social isolation measures were what achieved real flattening of the curve.
Professor Murphy, revealing the modelling at a media conference yesterday, said Australian measures to date already exceeded what was modelled in the more extreme distancing scenario and our actual data reflected that projected slowing.
“We know the tools we are using do work and we can scale them up and down as necessary,” he told journalists.
Professor McVernon told a media videoconference that it had soon been obvious “that unmitigated epidemics would be well beyond any high-income country’s healthcare system capacity”.
“The model informed the critical importance of public health response measures like case isolation and contact tracing, which have been and will continue to be a cornerstone of the Australian public health response,” she said.
Early measures bought time, but it was clear further measures would be needed, beyond what any country had planned for.
“So Australia … has implemented measures that would not have been considered many months ago. There was not a single pandemic plan globally that talks about lockdown as a control measure.
“We still are uncertain about the actual contributions of different measures that have been implemented in different settings and their contribution to reducing spread – things like school closure and workplace closure. We’re trying to unpick these from observations in Europe, but it’s still very unclear.”
Professor Vernon said they were now trying to understand the effects of Australian measures and work out next steps.
Her colleague Professor James McCaw, a mathematical biologist and infectious diseases epidemiologist, said the work had been led by the Doherty and Melbourne University but had involved at least five other institutions and had input from local and international working groups.
“We’re really in a very lucky position where we can think about the next steps and the very challenging questions ahead, from a position of relative calm as opposed to crisis,” he said.
“We don’t have an overwhelmed hospital system yet, and we may well never have one, if we continue to base our responses on the best available evidence.
“The next few weeks are absolutely crucial. With the increased caseload from the last few weeks, inevitably we’re going to see an increase in hospitalisations, admissions to ICU and deaths.
“And I think it’s really important at this time to realise that those will be driven by the past cases from the last few weeks. That increase is inevitable and it doesn’t mean that there’s a loss of control.”
Professor McCaw said the methods used were more conceptual and theoretical than the computational kind of modelling being done by others. Both approaches had strengths and weaknesses but also complemented each other.
And they both showed the same thing when it came to an easing off in social measures to curb the spread: “We know that our population is still largely susceptible. So if we relaxed and went back to normal, we would see a rapid and explosive resurgence in epidemic activity.”
He said the next round of official modelling using Australian data, as promised by the Prime Minister and Professor Murphy yesterday, was already under way and was different in scope.
“The first work we’ve done is like climate change, longterm [modelling],” Professor McCaw said. “And the work we’re pivoting to is more like the daily weather forecast, which changes every day.
“We will be updating and re-examining Australia’s data two or three times a week, possibly every day, depending upon how much change and activity there is. And we will be then providing these short-term forecasts around what we believe that transmission is, what we believe that a future burden on the health sector will be and how do they respond to that.
“That work will be updated regularly as often as it needs to be to make decisions. How the government chooses to report that back and at what frequency is a question for them.”
