Wastewater-based epidemiology during New Zealand's COVID-19 elimination response: real-world public health impact and economic evaluation

After more than a year without community transmission, a localised outbreak of COVID-19 occurred in Auckland, New Zealand, in August 2021. The response to this outbreak was supported by wastewater-based epidemiology (WBE) with over 5,000 wastewater tests from 217 locations across New Zealand. This study provides specific real-world examples of the use of WBE to detect pathogen circulation and to provide supporting evidence that transmission was absent or limited in a community, and how this can directly influence public health actions. Evidence of community transmission via positive wastewater tests informed the escalation of public health responses, while early identification of infection in communities with no known cases enabled targeted interventions that contributed to effective control and pathogen elimination from a community. The economic benefits of these responses, quantified in millions of NZ dollars per day, highlight the value of WBE at low disease incidence and emphasise the importance of detection patterns in interpreting results and supporting communication to the public regarding infection risk. WBE can be a highly impactful and cost-effective public health tool in the response to disease incursions. Pandemic preparedness must include plans for selecting appropriate WBE sampling locations and ensuring the capacity to analyse sufficient samples rapidly.