Evaluate the Pharmacokinetics, Safety, and Tolerability of Nirsevimab in Healthy Chinese Adults

Inclusion Criteria: 1. Age 18 to 45 years 2. Weight ≥ 45 kg and ≤ 110 kg and Body Mass Index of 19 to 26 kg/m2 3. Healthy Chinese subjects (both male and female) 4. Normotensive 5. Normal electrocardiogram (ECG) within 28 days prior to Day 1 Exclusion Criteria: 1. Acute illness at study entry (pre-dose on Day 1) 2. Fever ≥99.5°F (37.5°C) on day of dosing 3. Any drug therapy within 14 days prior to Day 1 (except contraceptives). 4. Receipt of immunoglobulin or blood products within 6 months prior to study entry. 5. Receipt of any investigational drug therapy within 120 days prior to investigational product dosing or planned to receive any investigational drug therapy within 150 days after investigational product dosing. 6. Previous receipt of any marketed or investigational mAb. 7. Previous vaccination against RSV. 8. History of immunodeficiency or receipt of immunosuppressive medications during the prior year. 9. History of asthma. 10. History of autoimmune disorder. 11. Evidence of any systemic disease on physical examination. 12. Evidence of infection with hepatitis A, B, or C virus, syphilis, or human immunodeficiency virus. 13. Any clinically significant abnormal laboratory assessments at screening. 14. Pregnant or nursing mother. 15. Alcohol or drug abuse