A Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of Adenovirus Serotype 26 Based Respiratory Syncytial Virus Pre-fusion (Ad26.RSV.Pre-F) Vaccine in RSV-Seronegative Toddlers 12 to 24 Months of Age

Inclusion Criteria:

- Participant who is seronegative for respiratory syncytial virus (RSV) within 42 days
prior to dosing

- Participant is the product of a normal term pregnancy greater than or equal to (>=)37
weeks, with a minimum birth weight of 2.5 kilogram (kg)

- Participant must be in good health without any significant medical illness on the
basis of physical examination, medical history, and vital signs performed at screening

- Participant has received all routine immunizations appropriate for his or her age
according to local guidelines

- Each participant's parent(s)/legal guardian(s) must have access to a consistent means
of contact either by telephone contact or email/computer

Exclusion Criteria:

- Participant's weight is below tenth percentile according to World Health Organization
(WHO) pediatric growth and weight charts

- Participant has any clinically significant acute or chronic medical condition (for
example, history of seizure disorders, bleeding/clotting disorder, autoimmune disease,
active malignancy, systemic infections, congenital heart disease, history of any
pulmonary condition requiring medication, atopy, reactive airway disease,
medically-confirmed wheezing, bronchoconstriction or treatment with a beta 2 agonist,
cystic fibrosis, bronchopulmonary dysplasia, chronic pulmonary disease,
medically-confirmed apnea, hospitalization for respiratory illness, or mechanical
ventilation for respiratory illness) that, in the opinion of the investigator, would
preclude participation

- Participant is in receipt of, or planning to receive, live attenuated vaccine (for
example, measles, mumps and rubella [MMR] or varicella, but excluding rotavirus
vaccine) within 28 days of each study vaccination (that is, before and after); other
vaccines (for example, influenza, pertussis, polio or rotavirus) should be given at
least 14 days before or 14 days after each study vaccination

- Participant has known or suspected immunodeficiency, such as known human
immunodeficiency virus (HIV) infection

- Participant has a known allergy to vaccines or vaccine components (including any of
the constituents of the study vaccine), or history of anaphylaxis or other serious
adverse reactions to vaccines or vaccine components (including any of the constituents
of the study vaccine). Participants with egg allergies can be enrolled