Economic evaluation of wastewater surveillance in Ontario, Canada, using COVID-19 as a case study.

Background: The COVID-19 pandemic has stimulated the use of wastewater surveillance (WWS) in Canada. Objective: To inform continued investment, the study assessed the cost-utility of WWS, alongside conventional surveillance, compared to conventional surveillance alone, using COVID-19 in Ontario as an example. Methods: This model-based cost-utility analysis measured WWS effectiveness by increased lead time of 1-10 days for public health response using the Ontario health system perspective. The model integrated SARS-CoV-2 transmission dynamics, SARS-CoV-2 RNA concentration in the sewage system, and disease progression. The analysis considered year-round surveillance with an outbreak occurring once in a decade, assuming WWS benefits accrue only in the outbreak year. At the individual-level, a lifetime time horizon was used and future health outcomes (quality-adjusted life years [QALYs]) and cost were discounted at 1.5%. The model was informed by population-based administrative data and was calibrated to real-world Ontario surveillance data. Results: For Omicron/BA.1-like outbreaks, a WWS program with a $15 million CAD/year budget maintained over 10 years would be cost-effective at a $50,000 CAD/QALY threshold if it detects an outbreak three or more days earlier, and cost-saving if it detects an outbreak 10 or more days earlier than conventional surveillance. For a less severe outbreak with lower transmission rates, e.g., XBB-like, the WWS program would be cost-effective if at least six outbreaks occur in a decade. Conclusion: The study findings suggest that long-term investments in WWS are likely cost-effective for low-frequency but high-impact outbreaks. Maintaining WWS infrastructure will enhance Canada's emergency preparedness for emerging and re-emerging pathogens.