Dengue viruses, which cause dengue fever and dengue shock syndrome, are a major cause of morbidity and mortality in several of the world's tropical and subtropical regions. The rDEN2/4delta30(ME) vaccine is a live attenuated dengue virus vaccine that may be protective against dengue virus serotype 2 (DEN2). The purpose of this study is to evaluate the safety and immunogenicity of the rDEN2/4delta30(ME) vaccine in healthy adults.