Background: Infants with cardiac disease or prematurity are at risk for severe illness caused by respiratory syncytial virus. Immune globulin with a high titer of antibodies against respiratory syncytial virus may offer infants and young children at risk protection from this serious, common respiratory illness.

Methods: We studied 249 infants and young children (mean age, eight months) who had bronchopulmonary dysplasia due to prematurity (n = 102), congenital heart disease (n = 87), or prematurity alone (n = 60). Respiratory syncytial virus immune globulin was given monthly to some of these children in either a high dose (750 mg per kilogram of body weight; n = 81) or low dose (150 mg per kilogram; n = 79); 89 controls received no immune globulin. Group assignments were random. Assessments of respiratory illness and management were conducted without knowledge of the children's group assignments.

Results: There were 64 episodes of respiratory syncytial virus infection: 19 in the high-dose group, 16 in the low-dose group, and 29 in the control group. In the high-dose group there were fewer lower respiratory tract infections (7, vs. 20 in the control group; P = 0.01), fewer hospitalizations (6, vs. 18 in the control group; P = 0.02), fewer hospital days (43, vs. 128 in the control group; P = 0.02), fewer days in the intensive care unit (P = 0.05), and less use of ribavirin (P = 0.05). In the low-dose group there was a significant reduction only in the number of days in the intensive care unit (P = 0.03). Adverse events during the 580 infusions were generally mild and included fluid overload (in five children), oxygen desaturation (eight), and fever (six). Six children died: three in the high-dose group, three in the low-dose group, and none in the control group (P = 0.15), but no death was attributed to the use of immune globulin or to illness caused by respiratory syncytial virus.

Conclusions: Administration of high doses of respiratory syncytial virus immune globulin is a safe and effective means of preventing lower respiratory tract infection in infants and young children at high risk for this disease.