The purpose of this study is to assess the safety and tolerability of 2 single doses of either 5*10^10 viral particles (vp) or 1*10^11 vp of Ad26.RSV.preF, administered intramuscularly to elderly adults given approximately 12 months apart.

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, and is willing and able to comply with all study procedures and adhere to the prohibitions and restrictions specified in this protocol
• Before randomization, a woman must be: postmenopausal - A postmenopausal state is defined as no menses for 12 months without an alternative medical cause; and not intending to conceive by any methods
• From the time of first vaccination until 3 months after the first dose of study vaccine, and from the second vaccination through 3 months after, a man who has not had a vasectomy (or if a vasectomy was performed less than 1 year ago and the absence of sperm cannot be verified)
• In the investigator's clinical judgment, participant must be either in good or stable health. Participants may have underlying illnesses such as hypertension, type 2 diabetes, hyperlipoproteinemia, or hypothyroidism, as long as their symptoms/signs are medically controlled. If they are on medication for a condition, the medication dose must have been stable for at least 12 weeks preceding vaccination and expected to remain stable for the duration of the study. Participants will be included on the basis of physical examination, medical history, vital signs, and 12-lead electrocardiogram (ECG) performed at screening
• Participant must be healthy on the basis of clinical laboratory tests performed at screening. If the results of the laboratory screening tests are outside the central laboratory normal reference ranges and additionally within the limits of toxicity Grades 1 or 2 according to the US Food and Drug Administration (FDA) toxicity tables (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 (>=) 38.0 degree celsius within 24 hours prior to the first dose of study vaccine; enrollment at a later date is permitted
• Participant has a serious chronic disorder, including severe chronic obstructive pulmonary disease or clinically significant congestive heart failure, requirement for supplemental oxygen, end stage renal disease with or without dialysis, clinically unstable cardiac disease, Alzheimer's disease, or has any condition for which, in the opinion of the investigator, participation would not be in the best interest of the participant (for example, compromise well-being) or that could prevent, limit, or confound the protocol-specified assessments
• Participant has had major surgery within the 4 weeks prior to randomization or has planned major surgery through the course of the study
• Participant has chronic active hepatitis B or hepatitis C infection, documented by hepatitis B surface antigen and hepatitis C antibody, respectively
• Participant has human immunodeficiency virus (HIV) type 1 or type 2 infection