The purpose of this study is to evaluate the safety and immunogenicity of a tetravalent dengue vaccine administered subcutaneously or intradermally. The hypotheses being tested in this study is whether or not a tetravalent dengue vaccine may be safely administered to healthy normal individuals by intradermal (ID) or subcutaneous (SC) injection and provide measurable levels of serum neutralizing antibodies against all four dengue virus serotypes. The study is also designed to compare safety and immunogenicity between routes of administration and dose levels. The primary objective of this study is to evaluate the safety and tolerability of a two-dose regimen tetravalent dengue vaccine administered either SC or ID to healthy adult volunteers. Two dose levels will be tested in a dose-escalation format. Safety and tolerability will be measured by conducting post-vaccination safety assessments including physical examinations, injection site examinations, adverse event monitoring, hematology, blood chemistry, and urine dipstick. The secondary objective of this study is to assess the immunogenicity of the vaccine, in terms of neutralizing antibodies, against all four dengue serotypes when administered at two dose levels by two routes of administration in healthy adults. Titers of serum neutralizing antibodies will be measured at pre-vaccination, after prime and boost vaccinations and assessed by comparing titers at the two dose levels as well as the two routes of administration. In addition, viremia deriving from the attenuated vaccine viruses will be measured on days 0 (baseline), 2, 4, 5/6, 7, 9, 11, and 14 after both prime and boost vaccinations. Levels of neutralizing antibodies will also be measured in samples to be obtained on days 180 and 270 for analysis and submission in a supplement to the study report. This study will enroll 72 healthy flavivirus-negative male and female subjects between the ages of 18 and 45.