Home Virus safety ‘There is no going back’: experts on what Australia’s Covid modelling reveals | Bill Bowtell and Catherine Bennett

‘There is no going back’: experts on what Australia’s Covid modelling reveals | Bill Bowtell and Catherine Bennett

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‘These reports are not final judgments’

The release of the Doherty Institute Covid vaccination modelling and the associated treasury modelling is commendable.

However, these reports are not final judgments.

Rather, they are just the first words in what must be a critical debate about how Australia should meet the rapidly evolving challenges of the Covid pandemic.

In a democratic society, the government can propose and argue for what it wishes. But the final decisions must be embodied in legislation that reflects the outcome of these debates, the well-informed views of the Australian people and then approved by Australia’s parliaments. Importantly, a key central assumption underpinning the modelling needs to be interrogated.

That is, should Australia abandon the Covid zero goal achieved about October 2020 and sustained until mid-June 2021 when Covid Delta smashed through the New South Wales government’s inadequate quarantine defences at Sydney airport?

The Doherty Institute modelling demonstrates that opening Australia’s borders at various levels of vaccination coverage will have significant consequences affecting the health, wealth and happiness of every Australian, their families and businesses.

Once the decision is made to abandon Covid zero, there is no going back. It is a one-way journey to join most of the rest of the world with their ineradicable levels of endemic Covid and now rapidly rising caseloads of Delta-driven infections and deaths.

Australia and New Zealand have time to consider all the ramifications of what might be done next. In doing so, they can take into account the lessons of the failing “live with Covid” experiment now playing out in NSW.

There must now be the most rigorous, open and honest analysis and debate around these next steps, informed but not determined by the assumptions and options contained in the Doherty and treasury models.

Bill Bowtell AO is an adjunct professor at UNSW and a strategic health policy consultant. He was an architect of Australia’s successful response to HIV/Aids and has contributed to the global and national response to HIV and other infectious diseases

‘The importance of haste’

The comprehensive 180-day modelling takes us from the level of vaccine coverage we were at on 12 July to the infection and hospitalisation rates forecast at 70%, and then 80%, vaccination coverage. The multi-stage exercise fed vaccine supply into a model mimicking the Australian population with Delta circulating. Epidemic dynamics were then entered into a further model that projected clinical outcomes, infections, hospitalisation, ICU admission and deaths. Importantly, this was then combined with modelling of transmission potential under different public health responses and human behaviour extracted from Australia’s own data.

We know all too well that Delta has set us back with its high transmission rates, but it is still sobering to see 70% vaccine coverage in those 16 years and older could be associated with 2,000 deaths over six months under the best, transmission reducing, vaccination strategy – focusing next on those 20 to 30 years of age who have the highest rates of transmission.

The good news is that public health responses, similar to NSW back in August 2020 (social distancing, some caps and density limits), should be enough to contain outbreaks without more severe restrictions or lockdowns once we get to 70% coverage. Its is worth reading through the technical report to see the detail of the settings that are assumed, as well as the pragmatic assumptions on how activities like contact tracing efficiency bend under the weight of high case numbers. Options to ease some restrictions for vaccinated people are under discussion for Phase C, but the modelling does not suggest much leeway given public health measures will still be relied on to maintain control. At 80%, things look better with a 5-fold decrease in deaths, though some reliance on public health interventions will remain.

This is the first phase of ongoing work that will continue to monitor assumptions including, most critically, vaccine uptake. There are no dates in the modelling or the plan, but current vaccination rates could get us to these targets before year’s end. This modelling emphasises how much more challenging the Delta variant is, and the importance of haste so that we don’t need to increase transmissibility in this model by allowing time for a more infectious variant to emerge.

Catherine Bennett is chair in epidemiology at Deakin University



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