A randomized, double-blind, palivizumab-controlled, multi-center, multi-national trial conducted during 2 Northern Hemisphere RSV seasons with an intervening season in the Southern Hemisphere. Each child only participated during a single RSV season. Approximately 6,600 children at risk for serious RSV disease were to be randomized in a 1:1 ratio to receive either 15 mg/kg of palivizumab or motavizumab by IM injection every 30 days for a total of 5 doses.