The cost of building an environmental surveillance system for typhoid

IntroductionThe typhoid conjugate vaccine is a safe and effective method for preventing Salmonella enterica serovar Typhi (typhoid) and the WHOs guidance supports its use in locations with ongoing transmission. However, many countries lack a robust clinical surveillance system, making it challenging to determine where to use the vaccine. Environmental surveillance is an alternative approach to identify ongoing transmission, but the cost to implement such a strategy is previously unknown. MethodsWe estimated the cost of an environmental surveillance program for thirteen potential protocols. Unit costs were obtained from research labs involved in protocol development and equipment information was obtained from manufacturers and expert opinion. The cost model includes thirteen components and twenty-seven pieces of equipment. We used Monte Carlo simulations to project total costs. ResultsTotal costs per sample including setup, overhead, and operational costs, range from $357-794 at a scale of 25 sites to $116-532 at 125 sites. Operational costs (ongoing expenditures) range from $218-584 per sample (25 sites) to $74-421 (125 sites). Eleven of the thirteen protocols have operational costs below $200 at this higher scale. Protocols with high up-front equipment costs benefit more from scale efficiencies. Sensitivity analyses show that laboratory labor, process efficiency, and the cost of consumables are the primary drivers of cost. ConclusionAt scale, environmental surveillance may be affordable, depending on the protocol chosen and the geographic context. Costs will need to be considered along with protocol sensitivity. Opportunities to leverage existing infrastructure and multi-disease platforms may be necessary to further reduce costs. Summary BoxO_ST_ABSWhat is already known?C_ST_ABSEnvironmental surveillance has been used for polio transmission surveillance to target vaccination campaigns to prevent outbreaks. Similarly, methods for typhoid environmental surveillance are being developed, and could be used to support vaccine introduction decisions, if they are accurate and affordable. What are the new findings?Across the scenarios examined, operational costs are between $74-584 per sample depending on the scale and protocol selected. Operational costs are 67-79% of total annualized costs across the same permutations. What do the new findings imply?Policymakers can use these estimates and understanding of the efficiency of scale benefits in order to design a surveillance system that balances total cost with surveillance sensitivity and geographic coverage.