Cost-effectiveness of wastewater and environmental monitoring of respiratory syncytial virus to guide universal infant immunoprophylaxis in Canada.

Aims: To compare the cost-effectiveness of wastewater and environmental monitoring (WEM) versus clinical surveillance (CS)-guided respiratory syncytial virus (RSV) prophylaxis programs in Canada.

Materials and methods: A cost-utility model was developed comprising two identical decision trees for RSV-WEM and RSV-CS. Within each tree, children could conservatively receive nirsevimab prophylaxis (71% coverage) or not at the start of the RSV season and subsequently experience an RSV-related hospitalization, medically-attended, non-hospitalized RSV-infection, or be uninfected/non-medically attended. All children could experience respiratory morbidity up to age 18 years, with higher rates following RSV-related hospitalization. All prophylaxis and RSV-related costs were identical for RSV-WEM and RSV-CS. No costs were assumed for RSV-CS; whereas a cost of CAD$12.31 per infant (infrastructure: CAD$4.07 plus sampling: CAD$8.24) was assumed if a new RSV-WEM system was initiated, with all infrastructure costs included in year 1. Predicated on data from the 2022-23 Ontario RSV season, RSV-WEM was assumed to provide a 15.1% benefit for earlier initiation of the prophylaxis program versus RSV-CS. Outcomes were modelled over an 18-year time horizon (1.5% discounting).

Results: RSV-WEM dominated (lower costs and higher utilities) RSV-CS and remained unaltered in all scenario analyses. Scenarios included: amortization of RSV-WEM infrastructure costs over 5 years; using existing WEM infrastructure for RSV detection; 25% reduction in extra cases identified by RSV-WEM; 50%-90% prophylaxis coverage based on real-world data; and 25% increase in the cost of RSV-WEM.

Conclusions: The integration of RSV-WEM appears a highly cost-effective strategy (vs RSV-CS exclusively) to guide the earlier launch of RSV seasonal prophylaxis in Canada.