A Study to Assess the Safety and Effectiveness of Palivizumab Administered to Children at High Risk of Severe Respiratory Syncytial Virus (RSV) Infection in the Russian Federation and the Republic of Belarus

Inclusion Criteria: Infants at high risk of severe RSV infection defined as fulfilling at least one of the following: * Infants born ≤ 35 weeks gestational age AND are ≤ 6 months of age at enrollment * Infants ≤ 24 months of age at enrollment AND with a diagnosis of bronchopulmonary dysplasia (BPD) (defined as oxygen requirement at a corrected gestational age of 36 weeks) requiring intervention/management (i.e., oxygen, diuretics, bronchodilators, corticosteroids, etc.) anytime within 6 months prior to enrollment * Infants ≤ 24 months of age at enrollment with hemodynamically significant CHD, either cyanotic or acyanotic, unoperated or partially corrected. Children with acyanotic cardiac lesions must have pulmonary hypertension (≥ 40 mmHg measured pressure in the pulmonary artery \[ultrasound acceptable\]) or the need for daily medication to manage hemodynamically significant CHD Exclusion Criteria (main exclusion criteria): * Hospitalization at the time of enrollment (unless discharge is anticipated within 14 days) * Mechanical ventilation (including continuous positive airway pressure, CPAP) at the time of enrollment * Life expectancy less than 6 months * Unstable cardiac or respiratory status, including cardiac defects so severe that survival is not expected or for which cardiac transplantation is planned or anticipated * Active respiratory illness, or other acute infection