A Study to Evaluate the Immune Response and Safety of GSK Biologicals' HPV-16/18 L1 VLP AS04 Vaccine/Cervarix TM Vaccine in Healthy Females Aged 15-25 Years

Inclusion Criteria: * Subjects who the investigator believes that they or their parents/guardians can and will comply with the requirements of the protocol should be enrolled in the study. * A female between, and including, 15 and 25 years of age at the time of the first vaccination. * Written informed assent obtained from the subject and informed consent obtained from the parent or guardian of the subject. * Healthy subjects as established by medical history and clinical examination before entering into the study. * Subjects must have a negative urine pregnancy test. * Subjects of childbearing potential at the time of study entry must be abstinent, or must be using adequate contraceptive precautions for 30 days prior to vaccination and must agree to continue such precautions for two months after completion of the vaccination series. Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) other than the study/ control vaccine within 30 days preceding the first dose of study/ control vaccine, or planned use during the study period. * Pregnant or breastfeeding. * Planning to become pregnant or likely to become pregnant. * Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose. * Planned administration/administration of a vaccine not foreseen by the study protocol within 30 days before and 30 days after the first dose of vaccine. However, the administration of routine vaccines up to 8 days before the first dose of study vaccine is allowed. Enrolment will be deferred until the subject is outside of specified window. * Previous administration of components of the investigational vaccine * Previous vaccination against HPV or planned administration of any HPV vaccine other than that foreseen by the study protocol during the study period. * Any medically diagnosed or suspected immunodeficient condition such as HIV infection based on medical history and physical examination. * History of thrombocytopenia or hemostatic disorder in which case the study vaccine should under no circumstances be administered intramuscularly. * History of allergic disease, suspected allergy or reactions likely to be exacerbated by any component of the study/control vaccines. * Hypersensitivity to latex. * Known acute or chronic, clinically significant neurologic, pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by previous physical examination or laboratory tests. * History of chronic condition(s) requiring treatment. * Administration of immunoglobulins and/or any blood product within three months preceding the first dose of study/control vaccine or planned administration during the study period. Enrolment will be deferred until the subject is outside of specified window. * Acute disease at the time of enrolment.