Increased Risk for Respiratory Syncytial Virus-associated, Community-acquired Alveolar Pneumonia in Infants Born at 31-36 Weeks of Gestation

Background: We compared hospitalization and pediatric intensive care unit (PICU) admission rates for community-acquired alveolar pneumonia (CAAP) and respiratory syncytial virus (RSV)-associated CAAP (RSV-CAAP) in non-RSV-immunized children < 24-month-old born at 31-36 weeks gestational age (GA) versus those born at term (> 36 weeks GA). Methods: Nasopharyngeal samples for RSV were obtained prospectively (2004-2011) during RSV season, from hospitalized children with radiographic-diagnosed CAAP. Soroka University Medical Center is the only hospital in the region, enabling population-based rate calculation. Relative risks (RR) and 95% confidence intervals (95% CI) were calculated comparing RSV-CAAP incidence in 31-36 weeks GA with > 36 weeks GA children. Results: CAAP hospitalization incidences (per 1000 population) were 23.6 and 9.4 (RR: 2.52; 95% CI: 2.13-2.68), respectively; the respective incidences of PICU admission for overall CAAP were 1.8 and 0.2 (RR: 7.88; 95% CI: 4.59-11.83). The RRs (and 95% CI) for RSV-CAAP hospitalizations and PICU admission rates were (after extrapolation) 15.2 and 5.8 (RR: 2.79; 95% CI: 2.31-3.06) and 1.1 and 0.1 (RR: 9.14; 95% CI: 4.93-16.96), respectively. In a multiregression analysis in patients with RSV-CAAP versus CAAP, 31-36 weeks GA was an independent risk factor for hospitalization (RR: 1.485; 95% CI: 1.03-2.14). Conclusions: Children < 24-month-old born at 31-36 weeks GA are at increased risk for hospitalization and PICU admission for both overall CAAP and RSV-associated CAAP compared with those born at > 36 weeks GA. Moreover, in late premature children, RSV represented a 50% increased risk for CAAP compared with infants born at term.