A Worldwide, Phase I, Dose-Escalating Study of a 3-Dose Regimen of the MRKAd5 (Clade B) Vaccine in Healthy Adults (V520-018)

Inclusion Criteria: * Subject is in good general health * Subject tests negative for Hepatitis B, Hepatitis C, and HIV * Subjects of reproductive potential agree to use an accepted method of birth control through the entire study Exclusion Criteria: * Subject has a recent history of fever at time of vaccination * Subject has received immune globulin or blood product 3 months prior to injection * Subject has been vaccinated with live virus vaccine 30 days prior to receipt of first dose * Subject has been vaccinated with inactivated vaccine with 14 days prior to receipt of first dose * Subject has a chronic medical condition that is considered progressive * Subject has history of malignancy * Subject weighs less than 105 lb. * Female subject is pregnant or breast feeding, Male subject is planning to impregnate during the first year of study * Subject has contraindication to intramuscular injection * Subject is unlikely or unwilling to adhere to lower risk sex practices during the course of the study * Subject has a tattoo on the deltoid region of the arm or the injection of Depo-Provera