Study of Safety, Reactogenicity and Immunogenicity of GlaxoSmithKline's (GSK)Respiratory Syncytial Virus (RSV)Maternal Unadjuvanted Vaccine in Healthy Pregnant Women (Aged 18 to 40 Years) and Their Infants

Inclusion Criteria

Maternal subjects

• Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
• Subjects who give written or witnessed/thumb printed informed consent after the study has been explained according to local regulatory requirements, and before any study specific procedures are performed. The informed consent given at screening should (consistent with local regulations / guidelines) either:
• include consent for both the maternal subject's participation and participation of the infant after the infant's birth, or
• include consent for the maternal subject's participation and expressed willingness to consider permitting the infant to take part after the infant's birth.
• Both mother and father should consent if local regulations/guidelines require it.
• Age 18 to 40 years, inclusive, when informed consent is given.
• Pre-pregnancy BMI 18.5 to 34.9, inclusive
• Healthy as established by medical history and clinical examination before entering into the study.
• At 28^0/7 to 33^6/7 weeks of gestation at the time of study vaccination (Visit 1), as established by last menstrual period (LMP) date corroborated by first or second trimester ultrasound examination (U/S).
• If LMP and U/S do not correlate, default to U/S gestational age assessment. The level of diagnostic certainty of the gestational age should be established by using the Global Alignment of Immunisation safety Assessment in pregnancy gestation age assessment tool
• Subject satisfying screening requirements
• Singleton pregnancy
• HIV negative, as assessed by local standard of care serologic tests conducted during the current pregnancy and before enrolment (Visit 1).
• No fetal genetic abnormalities.
• No significant congenital malformations, as assessed by level 2 ultrasound (also known as a fetal anomaly ultrasound scan or fetal morphology assessment) conducted after 18 weeks of gestation
• Willing to provide cord blood
• Willing to have the infant followed-up after delivery for a period of 12 months
• Does not plan after delivery to give the infant for adoption or place the infant in care Note that women whose pregnancies resulted from Assisted Reproductive Technologies may be enrolled if they meet all inclusion criteria and none of the exclusion criteria.

Infant subjects

• Live-born from the study pregnancy.
• Re-signed (confirmed) written or witnessed/thumb printed informed consent for study participation of the infant obtained from the infant's mother and/or father and/or legally authorized representative, as applicable by local law, before performing any study specific procedure.

Exclusion Criteria

Maternal subjects

Medical conditions

• History of allergic disease or reactions likely to be exacerbated by any component of the RSV vaccine
• Hypersensitivity to latex
• Significant complications in the current pregnancy such as:
• Gestational hypertension at ≥20 weeks of gestation in the absence of proteinuria in a woman with a previously normal blood pressure
• Gestational diabetes which is not controlled by diet and exercise
• Pre-eclampsia
• Eclampsia during current pregnancy
• Intrauterine growth restriction
• Placenta previa
• Placental abruption, placenta accreta/percreta/increta, chorioamnionitis or any abnormalities that in the opinion of Investigator can impair the maternal-fetal circulation
• Polyhydramnios
• Oligohydramnios
• Cervical suture in place
• Preterm labour or history of preterm labour in the current pregnancy
• Ongoing medical intervention to prevent preterm delivery or medical treatment for suspected preterm delivery
• Cholestasis
• Other pregnancy-related complications that in the Investigator's judgement would preclude participation of the subjects in an investigational vaccine trial or might pose risk to the subject due to participation in the study
• Significant structural abnormalities of the uterus or cervix
• History of prior stillbirth or neonatal death
• Histor