A Phase II Randomized, Double-Blind, Two-Period Cross-Over Study to Evaluate the Pharmacokinetics, Safety and Tolerability of a Liquid Formulation of Palizvizumab (MEDI-493, Synagis)

Inclusion Criteria: * The child must have been born at greater than or equal to 35 weeks gestation and be greater than or equal to 6 months of age at the time of randomization (child must be randomized on or before their 6-month birthday) * The child's parent or legal guardian must provide written informed consent; and * The child must be able to complete the follow-up visits on Study Days 30 and 60 within the protocol specified windows (±2 days) * Parent/legal guardian of patient has available telephone access. Exclusion Criteria: * Be hospitalized; * Birth hospitalization \> 6 weeks duration; * Be receiving mechanical ventilation at the time of study entry (including CPAP); * Bronchopulmonary dysplasia (BPD), defined as history of prematurity and associated chronic lung disease with oxygen requirement for \>28 days; * Congenital heart disease (CHD). (Children with medically or surgically corrected \[closed\] patent ductus arteriosus and no other CHD may be enrolled.) * Known renal impairment, hepatic dysfunction, chronic seizure disorder, or immunodeficiency; * Any of the following laboratory findings in blood obtained within 7 days prior to study entry: * BUN or creatinine \>1.5´ the upper limit of normal for age * AST (SGOT) or ALT (SGPT) \>1.5´ the upper limit of normal for age * hemoglobin \<9.0 gm/dL * white blood cell count \<4,000 cells/mm3 * platelet count \<110,000 cells/mm3 * Acute illness or progressive clinical disorder; * History of recent difficult venous access; * Active infection, including acute RSV infection; * Previous reaction to IGIV, blood products, or other foreign proteins; * Received within the past 120 days or currently receiving IGIV, other immunoglobulin products, or any investigational agents; * Have ever received palivizumab; * Currently participating in any investigational study; or * Previously participated in any investigational study of RSV vaccines or monoclonal antibodies.