Safety, Immunogenicity and Efficacy of GSK S. Aureus Candidate Vaccine (GSK3878858A) When Administered to Healthy Adults (Dose-escalation) and to Adults 18 to 64 Years of Age With a Recent S. Aureus Skin and Soft Tissue Infection (SSTI)

1 dose of Sa-5Ag (5 antigens of S. aureus) half dose, non-adjuvanted at Day 1, administered intramuscularly.

1 dose of Sa-5Ag (5 antigens of S. aureus) full dose, non-adjuvanted at Day 1, administered intramuscularly.

1 dose of Sa-5Ag (5 antigens of S. aureus) half dose, adjuvanted at Day 1, administered intramuscularly.

A series of 2 doses of S. aureus candidate vaccine (Sa-5Ag full dose adjuvanted) given approximately 2 months apart (Days 1 and 61), administered intramuscularly.

One dose of placebo (saline solution for injection/ vial or prefilled syringe) at Day 1 for placebo Groups 1 to 3 (Dose-escalation epoch) and a series of 2 doses of placebo given approximately 2 months apart (Days 1 and 61) for placebo Group 4 (Dose-escalation epoch) and Group PoP: Placebo, administered intramuscularly.