Respiratory Syncytial Virus Associated Hospitalizations in Infants of 33 to 42 Weeks' Gestation: Does Gestational Age Matter?

Abstract

To evaluate rates and characteristics of respiratory syncytial virus hospitalizations (RSV-H) in infants of 33 to 42 weeks of gestational age (GA). All infants with a history of neonatal hospitalization and a GA of 33 to 42 weeks born between 2005 and 2015 and follow-up at least over one RSV season (first year of life). Infants with congenital heart disease and other congenital anomalies were excluded. Retrospective single-center cohort STROBE compliant study. Data were collected regarding demographic data and re-hospitalization characteristics due to respiratory illness and due to RSV infection; and data were compared between moderate-late preterm, near term, term, and post term infants, respectively. A total of 81.656 live born infants were registered in our catchment area with gestational age from 33 to 42 weeks during the study period; and 2188 of 2356 preterm infants and 1004 of 1168 term infants with history of neonatal hospitalization were included for analysis. Rehospitalizations due to respiratory illness occurred in 301 preterm (13.8%) and 136 term (13.5%) infants for 381 and 183 times, respectively. In total 84 of 3192 infants (2.6%) were tested RSV positive, 61 of 2188 preterm (2.8%) and 23 of 1004 term (2.3%). Preterm infants without history of neonatal hospitalization had a RSV hospitalization (RSV-H) rate of 1.7% (61/3488) and term infants of 1.3% (967/74.644) that were significantly lower compared to study infants (p=0.004 and 0.002, respectively). Moderate and late preterm (2.8%), near term (3.1%) and post term (3.5%) infants had significantly higher RSV-H rates compared to term infants (1.2%). Risk factors for RSV-H in preterm infants included discharge during RSV season (4.2 vs. 2.0%, p=0.017) and presence of older siblings (4.2 vs. 2.1%, p=0.023), in term infants presence of older siblings (p=0.019). The course of RSV disease did not differ between groups. Interestingly, we did not observe decreasing RSV-H rates with increasing GA. Term infants represented the group with lowest RSV-H rates. Neonatal hospitalization was a risk factor for RSV-H for both preterm and term infants. Near term infants do more resemble the late preterm than term infants regarding RSV-H rates. We found comparable higher RSV-H rates in all groups compared to term infants without differences in the course of disease and identified neonatal hospitalization as an independent risk factor.