Abstract: A novel vaccine antigen for prevention of Respiratory Syncytial Virus (RSV) infection is created which surpasses conventional vaccines comprising as an antigen RSV F protein alone in view of efficacy and/or safety. A vaccine is prepared which comprises as an antigen a RSV F/G chimeric protein wherein a portion of RSV F protein as a basic structure is replaced with a whole or a portion of Conserved Central Domain sequence of RSV G protein or wherein a whole or a portion of Conserved Central Domain sequence of RSV G is added to the basic structure. As a result of assessment of both efficacy and safety, a vaccine comprising as an antigen the F/G chimeric protein of the present invention confirmed to be more excellent than a vaccine comprising as an antigen RSV F protein alone in view of efficacy and/or safety.