Initial modelling projections for second epidemic wave in Sydney, NSW

Diagnoses and hospitalisations in Sydney will continue increasing for several weeks before reaching a peak and declining once sufficient vaccine-acquired immunity is achieved.

Dr Romesh Abeysuriya, Dominic Delport, Dr Rachel Sacks-Davis, Professor Margaret Hellard, Dr Nick Scott

Objective:

Burnet’s modelling team were asked to provide projections to the NSW Government. The COVASIM model was used to simulate the greater Sydney population as two different units: the 12 LGAs of concern, and the rest of greater Sydney. The model has been calibrated on the NSW case numbers to date and vaccine roll-out, including an additional 530,000 doses of Pfizer vaccine delivered over three-week intervals for people aged 16-39 years in the 12 LGAs of concern. Data was also drawn from a variety of other sources including work-type, people movement, vaccine roll-out and uptake. It also took account of restrictions that were incrementally imposed in NSW, including ongoing lockdown and closure of non-essential services throughout Sydney, restrictions on mobility between the LGAs of concern and the rest of Sydney, and shorter lockdowns of regional areas in response to outbreaks. Vaccination rates have also been increased.

Findings:

Under current restrictions and projected vaccination numbers, diagnoses and hospitalisations in Sydney will continue increasing for several weeks before reaching a peak and declining once sufficient vaccine-acquired immunity is achieved.

The LGAs of concern are estimated to peak at a 7-day average of 1,129-1,967 between 13-20 September 2021, with hospital demand peaking at 2,222-3,938 over the same period.
Across all of greater Sydney, the 7-day average is estimated to peak at 1,219-2,046 between 13-20 September, with hospital demand peaking at 2,286-4,016 over the same period.
Responses implemented so far are estimated to have averted a substantive number of infections and deaths.
In the 12 LGAs of concern, without any restrictions being introduced or additional Pfizer doses there would have been an estimated 589,817 and 5,808 cumulative diagnoses and deaths respectively over Jun-Dec 2021.
The restrictions combined with the original vaccine roll-out have averted an estimated 488,020 infections and 4,830 deaths.
The additional 530,000 Pfizer doses are estimated to have averted an additional 24,267 diagnoses and 254 deaths.

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First published: Sep 7, 2021

Burnet Institute

The Burnet Institute is an Australian medical research institute that combines medical research in the laboratory and the field, with public health action to address major health issues affecting disadvantaged communities in Australia, and internationally.