A Study to Evaluate Different Dose Levels of GlaxoSmithKline (GSK) Biologicals' Investigational Respiratory Syncytial Virus (RSV) Vaccine (GSK3888550A), Based on the Vaccine Safety and the Antibodies (Body Defences) Produced Following Vaccine Administration, When Given to Healthy Non-pregnant Women

Inclusion Criteria

• Subjects who the investigator believes will comply with the requirements of the protocol (e.g. completion of the diary cards/questionnaires, return for follow-up visits, have regular contact to allow evaluation during the study);
• Written informed consent obtained from the subject;
• Healthy female subjects; as established by medical history and clinical examination, aged 18 to 45 years at the time of the vaccination;
• Female subjects of childbearing potential may be enrolled in the study, if the subject:
• has practiced adequate contraception for 30 days prior to vaccination, and
• has a negative pregnancy test on the day of vaccination, and has agreed to continue adequate contraception until 90 days after vaccination

Exclusion Criteria

• Use of any investigational or non-registered product other than the study vaccine within 30 days preceding vaccination or any planned use during the study period;
• Concurrently participating in the active phase of 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
• Chronic administration (defined as more than 14 days in total) of immunosuppressant or other immune-modifying drugs, as well as administration of long acting immune modifying drugs, within 6 months prior to the vaccine dose (for corticosteroids, this will mean prednisone higher than or equal to (≥) 5 milligrams per day (mg/day), or equivalent). Inhaled and topical steroids are allowed;
• Administration of immunoglobulins and/or any blood products during the period starting 3 months before the study vaccination, or planned administration until 90 days post-vaccination;
• 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;
• Presence of neurological or psychiatric diagnoses which, although stable, are deemed by the investigator to render the potential subject unable/unlikely to provide accurate safety reports;
• Family history of congenital or hereditary immunodeficiency;
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination;
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccine;
• Any acute or chronic, clinically significant disease, as determined by physical examination, laboratory screening tests, subject personal report and/or health care provider information. The following conditions will be exclusionary:
• Diabetes mellitus,
• Respiratory diseases, such as:
• Chronic Pulmonary diseases, including Chronic Obstructive Pulmonary Disease (COPD),
• Bronchopulmonary dysplasia (note: history of past bronchopulmonary dysplasia as a neonate/infant will not be exclusionary),
• Uncontrolled asthma or asthma necessitating treatment with chronic systemic glucocorticoids
• Significant and/or uncontrolled psychiatric illness:
• hospitalization for psychiatric illness, history of suicide attempt(s) or confinement for danger to self or others within 10 years
• clinically significant depression
• Major neurological disease including:
• seizure or adulthood epilepsy (note: history of febrile convulsion in childhood is not exclusionary)
• myasthenia gravis
• history of repetitive migraine mal/status migrainosus
• Significant cardiovascular disease, including:
• Uncontrolled arterial hypertension,
• Congenital heart disease (with the exception of corrected atrial or ventricular septal defects),
• Previous myocardial infarction,
• Valvular heart disease or history of rheumatic fever,
• Previous bacterial endocarditis,
• History of cardiac surgery (with the exception of corrected atrial or