Vaccine Against Respiratory Syncytial Virus

Eligibility Details: Inclusion Criteria: - Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol. - Written or witnessed/thumb printed informed consent obtained from the subject prior to performance of any study specific procedure. - Healthy female subjects; as established by medical history and clinical examination, aged 18 to 45 years at the time of the first 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 for 90 days after completion of the vaccination. - No local condition precluding injection in both left and right deltoid muscles. Exclusion Criteria: Medical conditions - History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccines; - Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination; - Hypersensitivity to latex; - Major congenital defects, as assessed by the investigator; - Acute or chronic clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by medical history, physical examination or laboratory screening tests; - Significant or uncontrolled psychiatric illness; - Recurrent history or un-controlled neurological disorders or seizures; - Documented HIV-positive subject; - History of or current autoimmune disease; - Body mass index > 40 kg/m^2; - Any clinically significant hematological laboratory abnormality. - The investigator should use his/her clinical judgement to decide which abnormalities are clinically significant. - Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the subject due to participation in the study. Prior/Concomitant therapy - Use of any investigational or non-registered product (drug, vaccine or medical device) other than the study vaccines during the period starting 30 days before the first dose of study vaccines (Day -29 to Day 1), or planned use during the study period; - Administration of long-acting immune-modifying drugs at any time during the study period; - Administration of immunoglobulins and/or any blood products or plasma derivatives during the period starting 3 months before the first dose of study vaccines or planned administration during the study period; - Chronic administration (defined as more than 14 days in total) of immunosuppressants or other immune-modifying drugs during the period starting 3 months prior to the first vaccine dose(s). For corticosteroids, this will mean prednisone ≥ 5 mg/day, or equivalent. Inhaled and topical steroids are allowed; - 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; - Administration of a vaccine containing diphtheria, tetanus or pertussis antigens or diphtheria and tetanus toxoids within the previous 5 years; - Previous experimental vaccination against RSV; Prior/Concurrent clinical study experience • 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 (drug or medical device); Other exclusions - Pregnant or lactating female; - Female planning to become pregnant or planning to discontinue contraceptive precautions; - History of alcoholism, drug abuse and/or use disorder within the past two years; - Any study personnel or their immediate dependents, family, or household members.