Burden of Severe Respiratory Syncytial Virus Disease Among 33–35 Weeks’ Gestational Age Infants Born During Multiple Respiratory Syncytial Virus Seasons

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Background: Moderate-late preterm infants, 33–35 weeks’ gestational age (wGA), are at increased risk for respiratory syncytial virus hospitalization (RSVH). The objective of this study is 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 to 2014. Infants’ 330–356 wGA without comorbidity born during the respiratory syncytial virus season who did not receive respiratory syncytial virus immunoprophylaxis were enrolled. Data for the first confirmed RSVH during the season (+1 month) were analyzed. Incidence and hospitalization rate per 100 patient-seasons, intensive care unit 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 per 100 patient-seasons was 4.52. Median hospital LOS was 5.7 days. A total of 22.2% of infants required intensive care unit admission for a median LOS of 8.3 days. A total of 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.