Effectiveness of palivizumab: evaluation of outcomes from the 1998 to 1999 respiratory syncytial virus season

Background Respiratory syncytial virus (RSV) remains a significant cause of morbidity, especially in premature infants and immunocompromised children, resulting in approximately 100 000 hospitalizations annually. A study was performed to evaluate the outcomes of those given palivizumab (Synagis; MedImmune, Inc., Gaithersburg, RID) during the 1998 to 1999 RSV season, its first season in general use. Methods.A retrospective chart review of 1839 patients from 9 United States sites was conducted, representing all patients given palivizumab at each site. Those evaluated were to have a gestational age of less than or equal to 35 weeks, were to be <2 years old at their first injection and were to have received at least one dose of palivizumab (humanized monoclonal antibody against RSV) between September, 1998, and May, 1999. Gestational age, comorbidities, frequency of injections, hospitalizations and length of hospital stays were assessed. Results. The antigen- or culture-positive RSV hospitalization rates for those given prophylaxis were 2.3% (42 of 1839) overall, 16/399 (4.0%) with chronic lung disease of infancy and 26 of 1227 (2.1%) born prematurely without chronic lung disease of infancy. Twenty-six patients had a gestational age of >35 weeks and were included in the analysis. Conclusions. Only 2.3% of children receiving palivizumab prophylaxis were hospitalized with RSV lower respiratory infection. This compares favorably with the rates observed in the pivotal trial (IMpact-RSV trial in 1996 to 1997), in which prophylaxis reduced hospitalization from 10.6% in the placebo group to 4.8% in those children receiving prophylaxis.