A Study to Evaluate the Safety, Reactogenicity and Immunogenicity of GSK Biologicals' Investigational Unadjuvanted RSV Maternal Vaccine Compared to Placebo When Administered to Healthy Non-pregnant Women.

• 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