Safety, Reactogenicity and Immunogenicity Study of Different Formulations of GlaxoSmithKline (GSK) Biologicals' Investigational RSV Vaccine (GSK3003891A), in Healthy Women

Inclusion Criteria: * Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol. * Written informed consent obtained from the subject prior to performing any study specific procedure. * Non-pregnant female between, and including, 18 and 45 years of age at the time of study vaccination. * Healthy subjects as established by medical history and clinical examination before entering into the study. * Female subjects of non-childbearing potential may be enrolled in the study. * Female subjects of childbearing potential may be enrolled in the study, if the subject: * Has practiced adequate contraception for 30 days prior to study vaccination, and * Has a negative pregnancy test on the day of study vaccination, and * Has agreed to continue adequate contraception during the study period. Exclusion Criteria: * Use of any investigational or non-registered product other than the study vaccine within 30 days prior to study vaccination, or planned use during the study period. * Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational vaccine/ product. * Any medical condition that in the judgment of the investigator would make intramuscular injection unsafe. * Planned administration/ administration of a vaccine not foreseen by the study protocol within the period starting 30 days before and ending 30 days after study vaccination, with the exception of any licensed influenza vaccine which may be administered ≥ 15 days before or after study vaccination. * Previous experimental vaccination against RSV. * History of any reaction or hypersensitivity likely to be exacerbated by any component of the study vaccines. * History of severe allergic reaction after a previous dose of any tetanus toxoid, diphtheria toxoid, or pertussis antigen-containing vaccine or to any component of Boostrix. * History of encephalopathy of unknown aetiology occurring within 7 days following a previous vaccination with pertussis-containing vaccine. * History of any neurological disorders or seizures * History of transient thrombocytopenia or neurological complications following a previous vaccination against diphtheria and/ or tetanus. * Chronic administration of immunosuppressants or other immune-modifying drugs within 6 months prior to study vaccination, or planned administration during the study period. Inhaled and topical steroids are allowed. * Administration of immunoglobulins and/ or any blood products within the 3 months prior to study vaccination, or planned administration during the study period. * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination. * Family history of congenital or hereditary immunodeficiency. * History of or current autoimmune disease. * Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality. * Malignancy within previous 5 years or lymphoproliferative disorder. * Current alcohol and/or drug abuse. * Acute disease and/ or fever at the time of enrolment. * Hypersensitivity to latex. * Pregnant or lactating female. * Planned move to a location that will prohibit participating in the trial until study end. * Any other condition that the investigator judges may interfere with study procedures or findings.