Modeling Zika Vaccination Combined With Vector Interventions in DoD Populations.

Abstract

Zika virus (ZIKV) is a mild febrile illness generally transmitted via the bite of infected Aedes species mosquitoes, including Aedes aegypti, with the potential to cause neurological complications. Nearly 200 U.S. military installations are located within areas where Aedes mosquitos are found, putting thousands of personnel at risk for infection with ZIKV. This analysis aims to quantify the benefits of interventions, including vaccination, to decrease the risk of ZIKV on U.S. military installations. The authors developed a dynamic transmission model to test the "effectiveness" of vaccination, personal protective measures (PPM), and mosquito control at reducing morbidity within U.S. military populations. ZIKV transmission was modeled as a compartmental susceptible-exposed-infected-recovered model tracking interactions between humans and mosquitos and incorporating seasonality of mosquito populations and the potential for herd immunity. The model included two-dose vaccination as well as symptomatic and asymptomatic infection. The model was calibrated against 2016 public health data in Puerto Rico; sensitivity analyses were performed on model parameters and interventions. The greatest reduction in total modeled ZIKV cases resulted from vaccination combined with mosquito control and PPM. All three interventions at their highest estimated level of efficiency reduced ZIKV cases by 99.9% over the baseline case of low-level adherence to PPM. The addition of vaccination had limited additional benefit over effective vector control and PPM since the significant lag to vaccine-induced protection limited effectiveness of vaccination. Given the current vaccine, the model predicted that up to 92.8% of Zika cases occurring in deployment settings over a 10-year period could be prevented by adding vaccination to current low-level PPM. Combining vaccination with other interventions can reduce cases further. A location-specific cost-benefit analysis would be a valuable contribution to outbreak control policy as it could evaluate the economic impact of the interventions versus the reduced level of illness and downtime in this setting.