Infection with human papillomavirus (HPV) has been clearly established as the central cause of cervical cancer. Vaccination of pre-teens and adolescents, ideally before sexual debut and thus before exposure to oncogenic HPV, is a rational strategy for prevention of cervical cancer, and so HPV vaccination could complement the existing pre-adolescent/adolescent vaccination programs. Therefore, this Phase IIIb study is designed to evaluate the safety and immunogenicity of co-administering a commercially available vaccine with GSK Biologicals' HPV-16/18 L1 AS04 (Cervarix ®) vaccine as compared to the administration of either vaccine alone. This Protocol Posting has been updated in order to comply with the FDA AA, Sept 2007.