Efficacy and Safety of Clesrovimab (MK-1654) in Infants (MK-1654-004)

Key Inclusion Criteria: * Is a healthy male or female who is an early or moderate pre-term infant (≥29 to 34 weeks and 6 days gestational age) or a late pre-term or full-term infant (≥35 weeks gestational age) * For the phase 2b cohort only: Has a chronological age \>2 weeks of age up to 1 year and is entering their first respiratory syncytial virus (RSV) season at the time of obtaining documented informed consent. * For the phase 3 cohort only: Has a chronological age from birth up to 1 year and is entering their first RSV season at the time of obtaining documented informed consent. * For participants in South Korea only: Weighs ≥2 kg Key Exclusion Criteria: * Is recommended to receive palivizumab per local guidelines or professional society recommendations. * Has known hypersensitivity to any component of clesrovimab * Has a bleeding disorder contraindicating IM administration * Has had a recent illness with rectal temperature ≥100.5°F (≥38.1°C) or axillary temperature ≥100.0°F (≥37.8°C) within 72 hours predose * Has received any vaccine or monoclonal antibody for the prevention of RSV * Is currently participating in or has participated in an interventional clinical study with an investigational compound or device at any time before first dose administration or while participating in this study