The most advanced candidate vaccine against dengue viruses, called CYD-TDV, is progressing toward potential registration and review by the World Health Organization (WHO) in 2016. CYDTDV is a formulation of four chimeric yellow fever 17D vaccine viruses, each one engineered to express the surface envelope and prM (membrane) proteins from one of the four serotypes of dengue virus. The surface envelope protein is a target of virus-neutralizing antibodies. (Editorial)