City-wide Surveillance for the Occurrence of Respiratory Syncytial Virus(RSV) Respiratory Tract Infections in a Population of High Risk Infants ≤32 weeks Gestational Age † 1453

Abstract

RSV IGIV has been recommended for use in high-risk infants ≤35 wks GA. In 1996, the following criteria were adopted for RSV IGIV use in all Level III NICUs in the City of Pittsburgh: 1) <1yr of age with chronic lung disease(CLD) - mechanical ventilation, supplemental oxygen, steroids and/or diuretics beyond 14 days of life, 2) ≤32 wks GA and <6 months chronologic age with high risk of non-preventable exposure to RSV (sibs in preschool or daycare). The purpose of this study was to determine the prevalence of RSV infection and the effectiveness of RSV IGIV in reducing RSV-associated hospitalization in a city-wide population of infants ≤32 wks GA. All infants born at ≤32 wks GA from 7/1/96-4/30/97 who met criteria were eligible to receive 1 to 6 doses of RSV IGIV (given monthly from 11/1/96-4/30/97). Parents were contacted at intervals through 6/30/97 to determine RSV IGIV treatment, occurrence of RSV infection and risk factors. We identified 282 infants ≤32 wks GA; 205 families were contacted (73%). Mean GA and birthweight were 29.5 wks ± 2.4 and 1338 g ± 402 respectively. Of the 53 infants eligible for RSV IGIV, 4 had no doses and 7 received IM RSV. Forty-two infants received 78% of eligible doses of RSV IGIV and one was hospitalized with RSV (2.4%). Twelve infants ineligible for RSV IGIV were hospitalized for RSV infection (8.1%). Of these 13 hospitalized infants, 9 had no recognized risk factors except prematurity, 1 had CLD (RSV-eligible, received 4 of 6 doses), 1 attended daycare and 2 had sibs in daycare or preschool. Mean age at hospitalization was 15 weeks ± 11 and mean length of stay was 8 days ± 8. Ten infants developed an oxygen requirement, 1 was ventilated. There were no infant deaths. We conclude that with 92% compliance with RSV IGIV administration in Pittsburgh using the above criteria, there was a decrease in RSV-associated hospitalization in at-risk infants ≤32 weeks with a case reduction rate of 70%. This study may indicate that current RSV IGIV administration criteria for treatment of high-risk infants ≤35 wks GA may be excessive. Cost analysis will be performed to determine the cost effectiveness of this strategy.