Results of clinical surveillance during the Japanese first palivizumab season in 2002–2003

Background: In Japan, palivizumab was approved in 2002 for prophylaxis of severe respiratory syncytial virus disease in high-risk infants. In order to evaluate the efficacy and safety of this drug, a questionnaire survey was conducted. Methods: A questionnaire was sent to member institutions of the Japan Neonatologist Association. The subjects were premature infants who were considered possible candidates for treatment with palivizumab. Results: A total of 6302 case reports, including those of 2806 infants receiving palivizumab (group P) and 3496 infants not receiving palivizumab (group NP), respectively, were retrieved. Background characteristics revealed significant lower gestational age (GA) and birthweight for group P (P < 0.0001). Sex ratio did not differ significantly, while use of oxygen and mechanical ventilation in the neonatal intensive care unit, and presence of chronic lung disease were significantly higher for infants in group P (P < 0.0001). When comparison of hospitalization rate for respiratory symptoms was performed with stratification by eligibility criteria, in the group of infants born at 29–35 weeks GA the hospitalization rate was 4.0% and 5.7% in groups P and NP, respectively (P < 0.05). Multivariate analysis also showed that prophylaxis with palivizumab was the only variable that significantly decreased rate of hospitalization (odds ratio 0.630, P= 0.0053). The incidence of adverse events associated with the administration of palivizumab was low. Conclusion: In this non-randomized questionnaire survey, multivariate analysis showed that palivizumab significantly decreased the rate of hospitalization due to respiratory symptoms for infants born prematurely at 29–35 weeks GA. These data confirmed the efficacy and safety of palivizumab.