More than 2 billion people living in tropical and subtropical regions of the world are at risk of dengue virus infection. Dengue viruses cause dengue fever, as well as the more severe dengue hemorrhagic fever/shock syndrome, and dengue virus infection is the leading cause of hospitalization and death in children in several tropical Asian countries. This study will evaluate the safety and immunogenicity of a live, attenuated dengue virus called rDEN3delta30/31-7164.~This study will consist of two groups, with Group 1 enrolling first. Group 1 participants will be randomly assigned to receive either 10^3 PFU of rDEN3delta30/31-7164 or placebo subcutaneously in their deltoid. Participants will be monitored at the clinic for 30 minutes after receiving the immunization to monitor for adverse effects. After that, participants will be asked to return to the clinic approximately every other day for the next 16 days, and then on Day 21, 28, 42, and 180. At each visit participants will have physical and clinical exams, vital signs, measures, blood drawn, and will be asked about any adverse events they may have experience. Female participants will be given a pregnancy test. In addition, participants will be asked to measure their temperature 3 times a day and record it in a temperature diary for the first 16 days after immunization.~If less than 90% of the participants in Group 1 seroconvert to DEN3 then Group 2A will be enrolled. Group 2A will follow the same procedures as Group 1, but will receive a 10^5 PFU dose of rDEN3delta30/31-7164.~If more than 90% of the participants in Group 1 seroconvert to DEN3 then Group 2B will be enrolled. Group 2A will follow the same procedures as Group 1, but will receive a 10^1 PFU dose of rDEN3delta30/31-7164.
Dengue fever, which is caused by dengue viruses, is a major health problem in tropical and subtropical regions of the world. The purpose of this study is to test the safety of and immune response to a new dengue virus vaccine in healthy adults.