An Exploratory 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

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.

Inclusion Criteria:

• Each participant must sign an Informed Consent Form (ICF) indicating that he or she understands the purpose of and procedures required for the study, is willing to participate in the study and attend all scheduled visits, is willing to be isolated and stay in the clinic for the quarantine phase, and is willing and able to comply with all study procedures and adhere to the prohibitions and restrictions specified in this protocol
• Participants must be in good health, without significant medical illness, on the basis of a medical evaluation that reveals the absence of any clinically relevant abnormality and includes a physical examination (including height and weight), skin examination, medical history, vital signs (systolic and diastolic blood pressure and heart rate, respiratory rate, and body temperature), and the results of clinical laboratory tests performed within 56 days of vaccination. If there are abnormalities, the participant may be included only if the investigator judges the abnormalities or deviations from normal to be not clinically significant. This determination must be recorded in the participant's source documents and initialed by the investigator
• Participants must have a non-clinically significant 12-lead electrocardiogram (ECG) within 56 days of vaccination including: normal sinus rhythm (heart rate between 50 and 100 beats per minute [bpm], extremes included); QT interval corrected for heart rate according to Fridericia (QTcF) interval less than or equal to (<=) 450 millisecond (ms); QT interval corrected for heart rate according to Bazett (QTcB) interval <= 450 ms; QRS interval less than (<) 120 ms; PR interval <= 210 ms
• Participants must be sero-suitable for respiratory syncytial virus (RSV) within 90 days of vaccination (low immunity to the RSV-A Memphis 37b virus using a virus neutralization assay
• Participant must be healthy on the basis of clinical laboratory tests performed within 56 days of vaccination. If the results of the laboratory screening tests are outside the local laboratory normal reference ranges and additionally within the limits of toxicity Grade 1 according to the US Food and Drug Administration (FDA) toxicity tables (that is, for tests in the FDA table), the participant may be included only if the investigator judges the abnormalities or deviations from normal to be not clinically significant and appropriate and reasonable for the population under study. This determination must be recorded in the participant's source documents and initialed by the investigator

Exclusion Criteria:

• Participant has acute illness (this does not include minor illnesses such as diarrhea) or temperature greater than or equal to (>=) 37.8 degree Centigrade within 24 hours prior to study vaccination
• Participant has history of malignancy (exceptions are basal cell carcinomas of the skin treated over 5 years prior to vaccination considered cured with minimal risk of recurrence)
• Participant has chronic active hepatitis B or hepatitis C infection, documented by hepatitis B surface antigen and hepatitis C antibody, respectively

Viral Challenge Exclusion Criteria:

• Participants having donated or lost more than 1 unit of blood (470 milliliter [mL]) within 60 days or more than one unit of plasma within 7 days
• Participants with active acute respiratory infection