The study included a dose-finding evaluation of a 3-dose regimen of V503 and GARDASIL, a safety/efficacy evaluation of a 3-dose regimen of the selected V503 dose formulation and GARDASIL, and an extension consisting of 2 substudies: an evaluation of immune memory in participants receiving a fourth vaccination with V503 (Cohort 1), and an opportunity for participants who received GARDASIL in the Base Study to receive a 3-dose regimen of V503 (Cohort 2).