Dengue viruses cause dengue fever and the more severe condition, dengue hemorrhagic fever/shock syndrome. Dengue viruses are common in most tropical and subtropical regions of the world and infection with dengue viruses is the leading cause of hospitalization and death in children in many tropical Asian countries. For these reasons, the World Health Organization (WHO) has made the development of a dengue virus vaccine a top priority. This study will evaluate the safety and immunogenicity of five versions of a live, attenuated, tetravalent dengue virus vaccine called TetraVax-DV.