Incidence of respiratory syncytial virus-related hospitalizations in high-risk children: follow-up of a national cohort of infants treated with Palivizumab as RSV prophylaxis.

The prophylactic administration of Palivizumab, a monoclonal antibody binding the respiratory syncytial virus (RSV) fusion protein, was recently shown to significantly decrease the incidence of RSV-related hospitalizations among high-risk children (IMpact-RSV trial). While awaiting marketing authorization in France and through a cohort of patients' name-based national program temporarily authorized by the French Drug Agency, a prospective register of all Palivizumab-treated patients in France was set up during the epidemic season 1999-2000. Based on this register, this study was carried out to evaluate the incidence of RSV-related hospitalizations and the safety of prophylaxis among a national cohort of children at high-risk of severe RSV disease. During the study period, guidelines issued by the French Pediatric Society recommended prophylaxis for children either aged less than 6 months at inclusion and born at less than 33 weeks of gestation with a history of bronchopulmonary dysplasia (BPD) at 28 days of life, or aged less than 2 years, born at less than 36 weeks of gestation, and having required treatment for BPD over the previous 6 months. Once included in the program, investigators were to prospectively report the clinical and demographic characteristics of children, all hospitalizations, and reasons for the hospitalizations. Five hundred and sixteen children were treated with 1-5 monthly doses. The median gestational age was 28 weeks, and children born at less than 33 weeks of gestation accounted for 88% of the cohort. The prevalence of BPD was 81%. Ninety children were hospitalized for respiratory illness. In 39 children, hospitalizations were attributed to RSV (7.6% of the total cohort). Among those 39 children, 10 (1.9% of the total cohort) required admission into an intensive care unit, and 4 required mechanical ventilation. No deaths or serious adverse events attributable to RSV infection or Palivizumab treatment were reported. We conclude that the RSV-related hospitalization rate in this high-risk cohort was comparable to the rate observed in the subgroup of Palivizumab-prophylaxed children with BPD in the IMpact-RSV trial.