Phase IIIb, Observer-blind Study to Compare Immunogenicity of GSK Biologicals' HPV-16/18 L1/AS04 Vaccine Versus Gardasil® [Quadrivalent Human Papillomavirus (HPV-6,11,16,18 L1 VLP) Recombinant Vaccine Merck & Co., Inc.]

Inclusion Criteria:

- A woman whom the investigator believes that she or her legally acceptable
representative (in the event that the subject is illiterate) can and will comply with
the requirements of the protocol (e.g., completion of the diary cards, return for
follow-up visits).

- A woman between and including 18 and 45 years of age at the time of the first
vaccination.

- Written informed consent must be obtained from the subject prior to enrollment.

- Subject must be free of obvious health problems as established by medical history and
history-directed clinical examination before entering into the study.

- Subject must have a negative urine pregnancy test.

- Subject must be of non-childbearing potential, or if she is of child bearing
potential, she must practice adequate contraception for 30 days prior to vaccination,
have a negative pregnancy test and continue such precautions for 2 months after
completion of the vaccination series.

- Subject must have an intact cervix.

Exclusion Criteria:

- Use of any investigational or non-registered product (drug or vaccine) other than the
study vaccine(s) within 30 days preceding the first dose of study vaccine, or planned
use during the study period up to Month 60.

- Chronic administration (defined as more than 14 days) of immunosuppressants or other
immune-modifying drugs within six months prior to the first vaccine dose or planned
administration during the study period up to Month 60.

- Planned administration/administration of a vaccine not foreseen by the study protocol
within 30 days before and 30 days after (i.e. days 0-29) each dose of vaccine.
Administration of routine vaccines up to 8 days before each dose of study vaccine is
allowed. Enrolment will be deferred until the subject is outside of specified window.

- Pregnant or breastfeeding. Women must be at least 3 months post-pregnancy and not
breastfeeding to enter the study.

- A woman planning to become pregnant or planning to discontinue contraceptive
precautions during approximately the first eight months of the study (Months 0-8).

- Previous administration of components of the investigational vaccine

- Previous or planned vaccination against HPV outside of this protocol.

- Any medically diagnosed or suspected immunodeficient condition based on medical
history and physical examination.

- History of allergic disease, suspected allergy or reactions likely to be exacerbated
by any component of the study vaccines.

- Hypersensitivity to latex.

- Known acute or chronic, clinically significant pulmonary, cardiovascular, neurologic,
hepatic or renal functional abnormality, as determined by previous physical
examination or laboratory tests.

- History of significant medical conditions and currently under treatment.

- Received immunoglobulins and/or blood product within 90 days preceding enrolment or
planned administration during the study period up to Month 60. Enrollment will be
deferred until the subject is outside of specified window.

- Acute disease at the time of enrolment. Enrollment will be deferred until condition
is resolved. All vaccines can be administered to persons with a minor illness

- Heavy bleeding (menstruation or other) or heavy vaginal discharge in which a pelvic
exam cannot be performed. Enrollment will be deferred until condition is resolved
according to investigator's medical judgement.