Cervical Intraepithelial Neoplasm (CIN) in Women (Gardasil) (V501-015)

The primary purpose of the study is to determine if GARDASIL™ (V501) is able to prevent cervical cancer.

In the 4-year Base Study (V501-015) (NCT00092534), participants were randomized in a 1:1 order to receive 3 doses of GARDASIL™ or matching placebo at Day 1, Month 2, and Month 6 and were assessed for efficacy, immunogenicity, and safety. In the Base Study Extension (EXT) \[V501-015-10\], participants who received placebo or only 1 dose of GARDASIL™ in the Base Study, were given 3 doses of open-label GARDASIL™ at EXT Day 1, EXT Month 2, and EXT Month 6, and were followed to EXT Month 7. Participants who who received 2 doses of GARDASIL™ in the Base Study were given 1 dose of GARDASIL™ at EXT Day 1 and were followed for 15 days (day of vaccination plus 14 days). In the 10-year Base Study Long-Term Follow-Up (LTFU) \[V501-015-21\] the effectiveness, immunogenicity and safety of GARDASIL™ was assessed during a period of 10 years following completion of the Base Study (V501-015) \[14 years after the first dose of GARDASIL™\] and, for some measures, the Base Study EXT (V501-015-10) \[10 years after the first dose of GARDASIL™\]. Participants from Denmark, Iceland, Norway and Sweden who participated in the Base Study were eligible to enroll in the LTFU. Effectiveness and safety was assessed by registry-based follow-up, and immunogenicity was assessed by serological testing at approximately Year 5 and Year 10 of the V501-015-21 LTFU. An 8-year extension was added to the LTFU (V501-015-22\] to continue the evaluation of the long-term effectiveness and immunogenicity of GARDASIL™. Effectiveness and safety will be assessed by registry-based follow-up, and immunogenicity will be assessed by serological testing at approximately Year 4 and Year 8 of the extension of the LTFU.