Estimating the Failure Risk of Quarantine Systems for Preventing COVID-19 Outbreaks in Australia and New Zealand

Objectives: To identify COVID-19 outbreaks and border control failures associated with quarantine systems in Australia and New Zealand and to estimate the failure risks. Design: , setting, participants: Observational epidemiological study of travellers transiting quarantine in Australia and New Zealand up to 15 June 2021. Main outcome measures: The incidence of COVID-19 related failures arising from quarantine, and the failure risk for those transiting quarantine, estimated both per 100,000 travellers and per 1000 SARS-CoV-2 positive cases. Results: : Australia and New Zealand had 32 COVID-19 related failures arising from quarantine systems up to 15 June 2021 (22 and 10, respectively). One resultant outbreak involved an estimated 800 deaths and quarantine failures instigated nine lockdowns. The failure risk for those transiting quarantine was estimated at 5.0 failures per 100,000 travellers and 6.1 failures (95%CI: 4.0 to 8.3) per 1000 SARS-CoV-2 positive cases. The latter risk was two-fold higher in New Zealand compared with Australia. The full vaccination of frontline border workers could likely have prevented a number of quarantine system failures. Conclusions: : Quarantine system failures can be costly in terms of lives and economic impacts such as lockdowns. Ongoing improvements or alternatives to hotel-based quarantine are required