[LINK] The Doherty Model

Stephen Loosley stephenloosley at outlook.com
Fri Aug 27 13:12:16 AEST 2021

If one may say, well done Richard. Thanks .. this would appear a fine situational awareness analysis.
And thanks for the correction.
Kind regards, Stephen

From: Richard Archer<mailto:rha at juggernaut.com.au>
Sent: Friday, 27 August 2021 11:22 AM
Subject: Re: [LINK] The Doherty Model

Since we're all now amateur epidemiologists, some other assumptions which caught my eye in the Doherty report:

p10: "partial TTIQ effectiveness" is based on 700 cases per day. At thousands of cases per day there will be effectively no "TTQ", just the "I" provided by lockdown measures.

p22: assumption that delta and alpha variants are equally severe. In contrast, the Sheikh paper referenced in the Doherty report finds delta is "associated with an increased risk of COVID-19 hospital admission: hazard ratio 1.85".

p30: assumption that children aged 5-14 show reduced onward transmission, seems to be invalidated by data from current Victorian outbreak

p40: assumption that cases are infected but not infectious for 2.5 days, data from Victorian outbreak suggests 1-1.5 days

p40: asymptomatic cases are 50% less transmissive, claimed without supporting data

p41: it is unclear whether deaths at home are modelled, or only deaths within the healthcare system

p20, table 5.6: This shows 5.4% of unvac <16 yrs developing a symptomatic infection but only 2.8% of unvac 16-39 yrs developing a symptomatic infection. This is clearly misleading and could be due to the 180 day limit on the forecast.

Each of the assumptions above result in the model predicting a much slower rate of transmission within the community. And therefore predicting a flatter curve, lower peaks, less strain on the health care system and greater effectiveness of TTIQ. These factors are all mutually reinforcing and synergise to produce a socially acceptable outcome.

While I acknowledge that we can't remain locked down forever, I am doubtful that the reality over the next 6 months will look anything like rosy picture painted by the Doherty modelling.

On the up side Stephen, Table S2.5 represents a 92% reduction in mortality rate from the starting point of approx 1%, so a final mortality rate of 0.1% rather than your interpretation of a total mortality rate of 8%.


On 2021-08-27 01:59, Stephen Loosley wrote:

The Doherty Model National Plan


Quote: (Page 13)

“Dynamics and consequences given timing of transition to Phase B

“Epidemic simulations assume a population size of 24 million. Infection outputs reflect the range of results observed across 20-30 separate model runs for each scenario. We assume that a single outbreak involving 30 individuals initiates community transmission at the time of transition to Phase B, once target vaccine coverage is achieved. Each simulation is run for 180 days after this initiating date ...

“Figure 2.1: Epidemic growth to 180 days given transition to Phase B leading to established community transmission for the threshold coverage targets of 50, 60, 70 and 80%, with vaccine allocation according to the ‘Oldest first’ strategy..”  (end quote)

Now, two of their four scenario graphs barely flatten off at 60,000 new infections a day after their 180 day study limit.

In other words ..

The Doherty Model does not even guess at our likely opened-up Phase B daily infection rates will be after six months ..  other than to note that the predicted infection rates will be something more than 60,000 people infected every day in Australia.

On Page 25, the Model for Delta predicts if everyone is fully vaccinated, between 8% and 10% of Australians will die.

That sounds like a wonderful plan for opening up, Mr Morrison.

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