A Study to Assess Safety, Pharmacokinetics Anti-Drug Antibody and Anti-RSV Antibody After 2 Doses of Nirsevimab

Participants in the first year of life will receive the 1st dose of nirsevimab as a single, fixed intramuscular (IM) dose of 50 mg if body weight is \<5 kg or 100 mg if body weight is ≥5 kg. A 2nd fixed IM dose of 50 mg if body weight is \<5 kg or 100 mg if body weight is ≥5 kg will be administered 5 to 6 months following the 1st dose.