The role of stocking constraints on the cost-effectiveness of vaccination against foot-and-mouth disease: The case of Scotland

Abstract

Purpose In developed country settings, a crucial debate has revolved around the merits of stamping out versus vaccination strategies to control foot-and-mouth disease (FMD), particularly given the tradeoffs associated with the loss of export markets under the latter. However, an overlooked issue concerns the logistics of a vaccination policy itself. For instance, in case of a large outbreak, it remains an open question as to whether sufficient vaccine stocks and delivery capacity for such stocks could be mobilized adequately to cost-effectively arrest the spread of disease. If delays in vaccine delivery are large, it is possible that the effects of these delays could not only undermine the success of a vaccination campaign but also impose significant costs on scarce veterinary resources. Methods In this paper, we analyze the potential impact of vaccination constraints on simulated outbreaks of FMD in Scotland. We use an epidemiological simulation model to consider different scenarios of capacity constraints and their effects on disease evolution and direct costs. Based on an initial seeding of five infected premises in a high risk area for disease spread, we examine the distribution of cases and costs associated with various capacity and restocking scenarios. Results When initial stocks are small (e.g. 100,000 doses), large restocking delays are of particular importance. While there was little difference in average costs whether restocking occurred 14 or 28 days after order, delays of 56 days and higher rapidly increased the direct costs of control. These delays in restocking nearly doubled the average days of disease duration, causing sharp losses associated with export bans in particular. Conclusion While maintaining high initial levels of stocks reduced the cost associated with an outbreak relative to no vaccination, one needs to consider the opportunity cost with maintaining large vaccine inventories. Relevance An important implication of the analysis concerns the tradeoffs between the optimal level of vaccine stocks pre-outbreak and the ability to obtain more during an outbreak, as well as the viability of a vaccination policy itself.