This is a Phase 2, randomized, double-blind study in which motavizumab (MEDI-524) and palivizumab will be administered to high-risk children during the same respiratory syncytial virus (RSV) season. It is anticipated that approximately 240 children (80 in each group) will be enrolled from the southern hemisphere during the upcoming RSV season (2006).

This is a Phase 2, randomized, double-blind study in which motavizumab and palivizumab will be administered to high-risk children during the same RSV season. It is anticipated that approximately 240 children (80 in each group) will be enrolled from the southern hemisphere during the upcoming RSV season (2006). Children will be randomized into one of three regimens in a 1:1:1 ratio; the first group will receive 2 doses of motavizumab followed by 3 doses of palivizumab; the second group will receive 2 doses of palivizumab followed by 3 doses of motavizumab; and the third group will receive 5 doses of motavizumab. Motavizumab or palivizumab will be administered at 15 mg/kg by IM injection every 30 days, for a total of 5 injections.

• Respiratory Syncytial Virus Infections
• Chronic Lung Disease

Inclusion Criteria:

• The child must have been born at less than or equal to 35 weeks gestation and be less than or equal to 6 months of age at the time of entry into the study (child must be entered on or before his/her 6-month birthday); or the child must be less than or equal to 24 months of age at the time of entry into the study (child must be entered on or before his/her 24-month birthday) and diagnosed with chronic lung disease (CLD) of prematurity with stable or decreasing doses of diuretics, steroids, or bronchodilators, or treatment with supplemental oxygen, within the previous 6 months.
• The child must be in general good health at the time of study entry.
• The child’s parent(s)/legal guardian must provide written informed consent.
• The child must be able to complete the follow-up visits through 120-150 days from last injection of study drug.
• Parent(s)/legal guardian of patient must have available telephone access.

Exclusion Criteria:

• Hospitalized at the time of study entry (unless discharge is expected within 10 days after entry into the study)
• Receiving chronic oxygen therapy or mechanical ventilation at the time of study entry (including continuous positive airway pressure [CPAP])
• Congenital heart disease (CHD) (children with medically or surgically corrected [closed] patent ductus arteriosus and no other CHD may be enrolled)
• Evidence of infection with hepatitis A, B, or C virus
• Known renal impairment, hepatic dysfunction, chronic seizure disorder, or immunodeficiency or HIV infection (a child of a mother with known HIV infection must be proven to be uninfected at the time of enrollment)
• Suspected serious allergic or immune-mediated events with prior receipt of palivizumab
• Acute illness or progressive clinical disorder
• Active infection, including acute RSV infection, at the time of enrollment
• Previous reaction to intravenous immunoglobulin (IGIV), blood products, or other foreign proteins
• Received within the past 120 days or currently receiving immunoglobulin products (such as RSV-IGIV [RespiGam], IVIG, or palivizumab) or any investigational agents
• Previous participation in a clinical trial of motavizumab
• Currently participating in any investigational study