A modelling analysis of the effectiveness of second wave COVID-19 response strategies in Australia

Abstract

There is a significant challenge in responding to second waves of COVID-19 cases, with governments being hesitant in introducing hard lockdown measures given the resulting economic impact. In addition, rising case numbers reflect an increase in coronavirus transmission some time previously, so timing of response measures is highly important. Australia experienced a second wave from June 2020 onwards, confined to greater Melbourne, with initial social distancing measures failing to reduce rapidly increasing case numbers. We conducted a detailed analysis of this outbreak, together with an evaluation of the effectiveness of alternative response strategies, to provide guidance to countries experiencing second waves of SARS-Cov-2 transmission. An individual-based transmission model was used to (1) describe a second-wave COVID-19 epidemic in Australia; (2) evaluate the impact of lockdown strategies used; and (3) evaluate effectiveness of alternative mitigation strategies. The model was calibrated using daily diagnosed case data prior to lockdown. Specific social distancing interventions were modelled by adjusting person-to-person contacts in mixing locations. Modelling earlier activation of lockdown measures are predicted to reduce total case numbers by more than 50%. Epidemic peaks and duration of the second wave were also shown to reduce. Our results suggest that activating lockdown measures when second-wave case numbers first indicated exponential growth, would have been highly effective in reducing COVID-19 cases. The model was shown to realistically predict the epidemic growth rate under the social distancing measures applied, validating the methods applied. The timing of social distancing activation is shown to be critical to their effectiveness. Data showing exponential rise in cases, doubling every 7–10 days, can be used to trigger early lockdown measures. Such measures are shown to be necessary to reduce daily and total case numbers, and the consequential health burden, so preventing health care facilities being overwhelmed. Early control of second wave resurgence potentially permits strict lockdown measures to be eased earlier.

SARS-CoV-2 Omicron disease burden in Australia following border reopening: a modelling analysis

“…That model was used to analyse the effectiveness of non-pharmaceutical social distancing interventions, varying their stringency, timing, and duration. 6,7 Our model was re-parameterised to reflect the transmission characteristics of the Delta variant following its emergence, and used to analyse a wide range of alternative vaccination strategies (October 2021). 8 These highlighted the importance of vaccinating children and adolescents, and determined vaccine coverage levels needed to reduce and prevent growth in case numbers, with and without reintroduction of social distancing measures.…”

“…The modelling analyses quantified infection and case reductions arising from increased vaccination coverage, and thus the reduction in hospitalisations and deaths. 7,8…”

“…The modelling analyses quantified infection and case reductions arising from increased vaccination coverage, and thus the reduction in hospitalisations and deaths. 7,8 For the purposes of estimating hospitalisations and deaths, infection data generated by the model was translated into cases using a 2:1 ratio, a proportion chosen to reflect estimated infection/case ratios in Australia in 2020, 11 in the absence of more recent Omicron-specific data. The relationship between case numbers, and hospitalisation and death numbers, were derived from case data using United Kingdom (UK) Omicron variant health burden datasets.…”

“…As described in prior studies, [6][7][8][9] our model represents every individual in the modelled community, together with their age. Each individual has an associated data structure to track their infection state (i.e.…”

Simulating Transmission Scenarios of the Delta Variant of SARS-CoV-2 in Australia

“…Several subsequent outbreaks were also detected and managed quickly and efficiently by contact tracing and local lockdowns, e.g., a cluster in the Northern Beaches Council of Sydney, New South Wales (NSW) totalled 217 cases and was controlled in 32 days by locking down only the immediately affected suburbs (December 2020-January 2021) (5). Overall, successful pandemic response was facilitated by effective travel restrictions and stringent stay-at-home restrictions (i.e., "social distancing, ") underpinned by a high-intensity disease surveillance (6)(7)(8)(9)(10).…”