An Exploratory, Phase 2a, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Prophylactic Efficacy of a Single Immunization of Ad26.RSV.preF Against Respiratory Syncytial Virus Infection in a Virus Challenge Model in Healthy 18 to 50 Year-Old Adults

The purpose of this study is to assess a trend for the prophylactic efficacy of a single dose of 1\*10\^11 virus particles (vp) of adenovirus serotype 26 respiratory syncytial virus pre-fusion F protein (Ad26.RSV.preF) administered intramuscularly to adults aged 18-50 years in the respiratory syncytial virus (RSV) challenge model in terms of reduction of nasal wash viral load compared to placebo.