Enhancing Mass Vaccination Programs with Queueing Theory and Spatial Optimization.

Background: Mass vaccination is a cornerstone of public health emergency preparedness and response. However, injudicious placement of vaccination sites can lead to the formation of long waiting lines or queues, which discourages individuals from waiting to be vaccinated and may thus jeopardize the achievement of public health targets. Queueing theory offers a framework for modeling queue formation at vaccination sites and its effect on vaccine uptake. Methods: We developed an algorithm that integrates queueing theory within a spatial optimization framework to optimize the placement of mass vaccination sites. The algorithm was built and tested using data from a mass canine rabies vaccination campaign in Arequipa, Peru. We compared expected vaccination coverage and losses from queueing (i.e., attrition) for sites optimized with our queue-conscious algorithm to those obtained from a queue-naive version of the same algorithm. Results: Sites placed by the queue-conscious algorithm resulted in 9-19% less attrition and 1-2% higher vaccination coverage compared to sites placed by the queue-naïve algorithm. Compared to the queue-naïve algorithm, the queue-conscious algorithm favored placing more sites in densely populated areas to offset high arrival volumes, thereby reducing losses due to excessive queueing. These results were not sensitive to misspecification of queueing parameters or relaxation of the constant arrival rate assumption. Conclusion: One should consider losses from queueing to optimally place mass vaccination sites, even when empirically derived queueing parameters are not available. Due to the negative impacts of excessive wait times on participant satisfaction, reducing queueing attrition is also expected to yield downstream benefits and improve vaccination coverage in subsequent mass vaccination campaigns.

Optimizing the location of vaccination sites to stop a zoonotic epidemic.

Mass vaccinations are crucial public health interventions for curbing infectious diseases. Canine rabies control relies on mass dog vaccination campaigns (MDVCs) that are held annually across the globe. Dog owners must bring their pets to fixed vaccination sites, but sometimes target coverage is not achieved due to low participation. Travel distance to vaccination sites is an important barrier to participation. We aimed to increase MDVC participation in silico by optimally placing fixed-point vaccination locations. We quantified participation probability based on walking distance to the nearest vaccination site using regression models fit to participation data collected over 4 years. We used computational recursive interchange techniques to optimally place fixed-point vaccination sites and compared predicted participation with these optimally placed vaccination sites to actual locations used in previous campaigns. Algorithms that minimized average walking distance or maximized expected participation provided the best solutions. Optimal vaccination placement is expected to increase participation by 7% and improve spatial evenness of coverage, resulting in fewer under-vaccinated pockets. However, unevenness in workload across sites remained. Our data-driven algorithm optimally places limited resources to increase overall vaccination participation and equity. Field evaluations are essential to assess effectiveness and evaluate potentially longer waiting queues resulting from increased participation.

Efecto del sacrificio de perros vagabundos en el control de la rabia canina / Effect of free-roaming dogs culling on the control of canine rabies

RESUMEN En la ciudad de Arequipa, Perú, se han detectado perros con rabia desde marzo de 2015, señal de la reintroducción del virus de la rabia (VR) en esta zona previamente declarada libre de esta enfermedad. La alta densidad de perros vagabundos ha sido considerada una de las causas de la continua transmisión del VR en el brote de la ciudad de Arequipa, alentando el sacrificio de perros como medida de salud pública. Sin embargo, la efectividad de esta medida de control no ha sido evaluada. El objetivo de esta revisión fue determinar la efectividad del sacrificio de perros vagabundos como medida de control de la rabia urbana. Se realizó la búsqueda de artículos sobre control de rabia canina o urbana en las bases de datos de Medline, Scopus y LILACS. Se incluyeron estudios originales y revisiones que hayan evaluado algún efecto del sacrificio de perros en la transmisión del VR. Veinte de 21 artículos concluyen que el sacrificio de perros vagabundos es inefectivo en reducir la trasmisión del VR e, incluso, puede tener consecuencias imprevistas que empeoren el problema. En conclusión, la evidencia disponible indica que sacrificar perros vagabundos no es efectivo para controlar la rabia urbana. Además, las diversas consecuencias negativas del sacrificio de los perros vagabundos reportadas en otras partes del mundo sugieren que el sistema de rabia urbana es altamente complejo y todos sus componentes deben ser tomados en cuenta durante la implementación de actividades de control.

ABSTRACT In the Peruvian city of Arequipa, rabid dogs have been detected since March 2015, signaling the reintroduction of the rabies virus (RV) in this previously officially-declared rabies free zone. High dog density is considered one of the causes for the continuous transmission of the RV in the outbreak in the city of Arequipa, which seemingly lends support to the culling of dogs as a public health measure. However, the effectiveness of culling free-roaming dogs to control urban rabies has not been evaluated. Objective to determine the effectiveness of free-roaming dog culling as a control measure of urban rabies. Source of data: We searched for articles on dog rabies control or urban rabies control in the databases of PubMed, Scopus and LILACS. The characteristics and results of the documents obtained were recorded. Eligibility criteria: We included original studies and reviews that have evaluated an effect of culling dogs in the transmission of RV. Data collection and evaluation: One of the authors (RCN) screened the articles found in the search based on their titles and abstracts. The data and results of the articles selected for full reading were evaluated by at least two authors. Results: 21 articles were eligible for full reading. 20 of 21 articles conclude that free-roaming dog culling is ineffective in reducing the transmission of RV and may even have unintended consequences that worsen the problem. We believe that the available evidence indicates that the sacrifice of free-roaming dogs is not effective to control urban rabies. In addition, the various negative consequences of free-roaming dog culling reported in other parts of the world suggest that the system of urban rabies is highly complex and all its components must be taken into account during the implementation of control activities.