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traQ Study: Transparent Risk Assessment of Quarantine

This study uses a mathematical model to examine the circumstances in which quarantine for COVID-19 could be reduced from 14 days without substantially increasing the risk of virus transmission.

The model identifies and quantifies relevant risk factors and considers combinations of increased testing, combined with other mitigation strategies, such as mask wearing and contract tracing.

Specific objectives are to:

  • Estimate the probability of onward transmission from international arrivals undergoing hotel quarantine in Australia to define a level of risk that is acceptable to the community.
  • Estimate the probability of onward transmission from domestic interstate travellers undergoing hotel quarantine.
  • Estimate the risk, associated cost and benefit, and uncertainty of these estimates for a range of scenarios regarding pre-test probability of exposure, age distribution, quarantine duration and test strategy, as well as identifying key parameters contributing to uncertainty in these estimates.


It is important to note that the relative risk of infection during travel, and for flying through hubs vs flying direct, are still being estimated. In addition, the estimates provided for scenarios and “average risks” for travellers, and particularly contacts of known cases, are illustrative and are still being refined. While we are confident that the relative risk of ongoing infection after 14-day quarantine is lower for those quarantined due to travel compared to those quarantined due to contact with a known case, the specific estimates are still being refined.

In addition, our current assumptions around standard testing and setting for quarantine of community-acquired cases are based on Victorian policy. We are in the process of checking policies in other states and territories.


An initial framework for modelling was developed and an advisory committee was established. The independent advisory committee providing input to the study has representatives from across Australia and across key stakeholder groups, including government. Insights into individual stakeholder groups will be most valuable when looking at various mitigation scenarios.

The advisory committee includes:

  • Sonya Bennett, CDNA Chair, Queensland Health
  • Alex Brown, Theme Leader, Aboriginal Health Equity, South Australian Health and Medical Research Institute (SAHMRI)
  • Dr Michael Kidd, Deputy Chief Medical Officer, Australia
  • Alison Morehead, Deputy – Strategy, National Mental Health Commission
  • Fiona Simson, President, National Farmers Federation
  • Ian Anderson, Australian National University.

Find out more about the Optimise Study

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Square Margaret Hellard 210X210

Professor Margaret Hellard AM

Contact Professor Margaret Hellard AM for more information about the project


Funding Partners

  • Minderoo Foundation