Health interventions often result in positive externalities that are not captured in traditional cost-effectiveness analysis. My research uses a dynamic transmission model to analyze the cost-effectiveness of preventing infections by the mosquito transmitted chikungunya virus. I compare a potential chikungunya vaccine to mosquito control methods that result in fewer chikungunya, zika, and dengue cases. By using this model, the additional health benefits of interventions that impact multiple diseases can be captured. These results will be used to better assess the total health benefits of proposed policies. It is important to account for these positive externalities to accurately compare targeted health interventions with policies that aim to improve overall health.