Phase I/II, Observer-blind, Safety, Reactogenicity and Immunogenicity Study of GSK Biologicals' Respiratory Syncytial Virus (RSV) Vaccine GSK3844766A in Subjects Aged 18-40 or 60-80 Years

The purpose of this study is to assess the safety, reactogenicity and immune responses of two
doses of the investigational RSV vaccines (with different formulations), when administered
intramuscularly (IM) according to a 0, 2 month schedule, in older adults aged 60 to 80 years.

As the investigational vaccines have not yet been tested in humans before, the study will
first assess the safety, reactogenicity and immune responses in young adults aged 18 to 40
years. The study will thus be conducted in 2 parts (Part A and Part B).