Respiratory Syncytial Virus (RSV) Investigational Vaccine in Infants Aged 6 and 7 Months Likely to be Unexposed to RSV

1 dose of RSV (GSK3389245A) lower dose formulation vaccine administered intramuscularly at Day 1.

2 doses of RSV (GSK3389245A) higher dose formulation vaccine administered intramuscularly, at Day 1 and Day 31.

3 doses of GSK's multicomponent meningococcal B vaccine administered intramuscularly, at Day 61, Day 121 and at the end of RSV season 1, or at Day 1, Day 61 and end of RSV season 1, depending on the vaccination schedule.

3 doses of Pfizer's meningococcal group A, C, W-135 and Y conjugate vaccine administered intramuscularly, at Day 61, Day 121 and at the end of RSV season 1, or at Day 1, Day 61 and end of RSV season 1, depending on the vaccination schedule.

3 doses of GSK's pneumococcal polysaccharide conjugate vaccine administered intramuscularly, at Day 61, Day 121 and at the end of RSV season 1, or at Day 31, Day 61 and end of RSV season 1, depending on the vaccination schedule.

2 doses of GSK's meningococcal group A, C, W-135 and Y conjugate vaccine administered intramuscularly, at Day 61 and at the end of RSV season 1, or at Day 31 and end of RSV season 1, depending on the vaccination schedule.

1 dose or 2 doses of Placebo administered intramuscularly at Day 31, or at Day 1 and Day 31, or at Day 1 and Day 61, or at Day 31 and Day 121, depending on the vaccination schedule.