Study to Assess the Immune Reactivity of the Liquid and Lyophilized Formulations of Palivizumab (MEDI-493, Synagis)

Inclusion Criteria: * Medically stable child with chronic lung disease of prematurity who is ≤24 months of age at randomization OR child with premature birth (gestational age ≤35 weeks or less) and who is 6 months of age or younger at randomization * Written informed consent obtained from the patient's parent(s) or legal guardian(s) * The child must be able to complete the follow-up visit 4-6 months after the last dose of study drug Exclusion Criteria: * Hospitalization at the time of randomization (unless discharge is anticipated within 3 weeks) * Be receiving mechanical ventilation at the time of study entry (including CPAP) * Congenital heart disease (children with uncomplicated CHD \[e.g., PDA, small septal defect\] and children with complicated CHD who are currently anatomically and hemodynamically normal can be enrolled). * Mother with HIV infection (unless the child has been proven to be not infected) * Life expectancy \<6 months * Known allergy to Ig products * Acute respiratory or other acute infection or illness * Previous reaction to IGIV, blood products, or other foreign proteins * Receipt of lyophilized palivizumab, RSV-IG IV, or other RSV-specific monoclonal antibody, or any other polyclonal antibody (for example, Hepatitis B IG, IVIG, VZIG) within 3 months prior to randomization * Any previous receipt of MEDI-524 * Participation in other investigational drug product studies