Burden of Severe Respiratory Syncytial Virus Disease Among 33-35 Week Gestational Age Infants Born During Multiple Respiratory Syncytial Virus Seasons

BACKGROUND:: Moderate-late preterm infants, 33-35 weeks’ gestational age (wGA), are at increased risk for respiratory syncytial virus hospitalization (RSVH). OBJECTIVE:: To quantify the burden of RSVH in moderate-late preterm infants. METHODS:: A pooled analysis was conducted on RSVH from 7 prospective, observational studies in the Northern Hemisphere from 2000-2014. Infants’ 33 -35 wGA without comorbidity born during the RSV season who did not receive RSV immunoprophylaxis were enrolled. Data for the first confirmed RSVH during the season (+1 month) were analyzed. Incidence and hospitalization rate/100 patient-seasons, intensive care unit (ICU) admission and length of stay (LOS), oxygen support, mechanical ventilation, and overall hospital LOS were assessed. RESULTS:: The pooled analysis comprised 7,820 infants; 267 experienced a confirmed RSVH at a median age of 8.4 weeks. The crude pooled RSVH incidence rate was 3.41% and the rate/100 patient-seasons was 4.52. Median hospital LOS was 5.7 days. 22.2% of infants required ICU admission for a median LOS of 8.3 days. 70.4% received supplemental oxygen support for a median of 4.9 days, and 12.7% required mechanical ventilation for a median of 4.8 days. CONCLUSIONS:: The burden of RSVH in moderate-late, 33-35 weeks’ wGA preterm infants without comorbidities born during the viral season in Northern Hemisphere countries is substantial. Severe cases required prolonged and invasive supportive therapy.