SAN DIEGO, CA—Preterm infants who do not receive respiratory syncytial virus immunoprophylaxis (RSV IP) frequently suffer severe RSV infection and ICU admission, according to findings reported at IDWeek 2015 from the observational multi-institutional SENTINEL 1 study.

“Among preterm infants born at 29–35 wGA (weeks’ gestational age) not receiving RSV IP, RSV illness can be severe, frequently resulting in ICU admissions and the need for mechanical ventilation, particularly during the first 6 months of life,” reported lead study author Leonard R. Krilov, MD, of Winthrop University Hospital in Mineola, NY, and coauthors.

In 1998, the monoclonal antibody palivizumab was approved to help prevent hospitalizations in preterm infants ≤35 wGA due to serious lower respiratory tract disease caused by RSV. However, recent data have shown that compared with full-term infants of the same chronologic age, those 32–35 wGA not receiving RSV IP have 2–3 times the risk of RSV-related hospitalization.

Therefore, the objective of the ongoing SENTINEL1 study “is to characterize RSV-confirmed hospitalizations among US preterm infants born at 29–35 wGA not receiving RSV IP during the 2014–2015 and 2015–2016 seasons,” Dr. Krilov noted.

During the 2014–2015 RSV season, defined as October 1, 2014 through April 30, 2015, data for 709 preterm infants with laboratory-confirmed RSV hospitalizations before the age of 1 year were collected at 43 sites. Only those hospitalized ≥24 hours and who did not receive RSV immunoprophylaxis within 35 days before onset of disease symptoms were included in the study. Infant wGA (29–32, 33–34, and 35), birth month, hospital length of stay (LOS), ICU admission, ICU LOS, mechanical ventilation, and survival were recorded for analysis. Exploratory statistical comparisons were conducted using the Wilcoxon rank-sum test.

“Overall, among the 709 infants 29–35 wGA, 295 (42%) were admitted to the ICU and 140 (20%) required mechanical ventilation,” Dr. Krilov reported.

Median age for ICU admission was 3 months (range, 2–5 months) among infants 29–32 wGA (n=243) compared with 2 months (range, 1–4 months) for infants 33–34 wGA (n=279; P<0.001) and 2 months (range, 1–5) for those 35 wGA (n=187; P<0.01). Among all admissions, mechanical ventilation was required in 25% of those 29–32 wGA, 19% in those 33–34 wGA, and 14% in those 35 wGA. Median hospital LOS and ICU admission were statistically significant when the 29–32 wGA group was compared with the 35 wGA group (P<0.001).

Consistent with previous RSV hospitalization studies, “earlier gestational age and younger chronologic age were associated with a higher risk of ICU admission and need for mechanical ventilation compared with birth at later gestational age and older chronologic age,” Dr. Krilov emphasized. “The incidence of RSV hospitalization was higher at younger chronologic age and at earlier gestational age.”

One 29-wGA infant died, a “male twin hospitalized at 2 months of age with community-acquired RSV disease and no reported comorbidities,” the authors reported.