Publications & Reports

Critical timing and extent of public health interventions to control outbreaks dominated by SARS-CoV-2 variants in Australia: a mathematical modelling study.

Zou Z, Fairley CK, Shen M, Scott N, Xu X, Li Z, Li R, Zhuang G, Zhang L
China-Australia Joint Research Centre for Infectious Diseases, School of Public Health, Xi'an Jiaotong University Health Science Centre, Xi'an, 710061, China.


OBJECTIVES: The exact characteristics of a COVID-19 outbreak that trigger public health interventions are poorly defined. We aimed to assess the critical timing and extent of public health interventions to contain COVID-19 outbreaks in Australia. METHODS: We developed a practical model using existing epidemics data in Australia. We quantified the effective combinations of public health interventions and the critical number of daily cases for intervention commencement under various scenarios of changes in transmissibility of new variants and vaccination coverage. RESULTS: In the past COVID-19 outbreaks in four Australian states, the number of reported cases on the day that interventions commenced strongly predicted the size and duration of the outbreaks. In the early phase of an outbreak, containing a wildtype-dominant epidemic to a low level (</=10 cases/day) required effective combinations of social distancing and face mask use interventions to be commenced before the number of daily reported cases reaches 6 cases. Containing an Alpha-dominant epidemic would require more stringent interventions that commenced earlier. For Delta variant, public health interventions alone will not contain the epidemic unless with vaccination coverage of >/=70%. CONCLUSIONS: Our study highlights the importance of early and decisive action in the initial phase of an outbreak. Vaccination is essential for containing variants.

Link to publisher’s web site


  • Journal: International Journal of Infectious Diseases
  • Published: 01/02/2022
  • Volume: 115
  • Pagination: 154-165