Public Health Policy making process is usually supported by traditional methods to assist the evaluation, like pseudo-evaluation methods and formal evaluation methods, to name but a few. In this paper, we propose the adoption of a Big Data platform supporting the definition and evaluation of a Public Health Policy allowing evidence-based analysis and reducing the need of costly clinical trials. The paper presents a formalized Public Health Policy in deontic logic form, the methodology of the policy making process, and the structure of the Big Data platform implementing the methodology. Concluding, we carried out a preliminary evaluation on a real case study demonstrating the benefits of our approach.