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Researchers identify risk factors for RSV disease in preterm infants
Preterm infants are at “substantially elevated risk” for respiratory syncytial virus disease, and chronologic age and exposure to other young children are the greatest risk factors, according to a study published in PLoS ONE.
“For RSV hospitalization and ICU admission, exposure to young children was associated with an increased risk, but the major predictor of risk was young chronologic age, consistent with severe RSV disease being driven by anatomical and physiologic vulnerability,” Eric A. F. Simões, MD, professor of pediatrics in infectious diseases at the University of Colorado School of Medicine, and colleagues wrote.
Researchers aimed to estimate RSV–related outpatient lower respiratory illness (LRI), hospitalization and ICU admission as a function of chronologic age among U.S. preterm infants with and without significant exposure to young children, based on birth month and age of exposure.
They analyzed data from the RSV Respiratory Events Among Preterm Infants Outcomes and Risk Tracking (REPORT) study, in which infants born from 32 to 35 weeks gestational age were followed from September to May of 2009-2010 or 2010-2011 at 188 U.S. clinics. RSV rates were determined by viral testing of infants with medically-attended acute respiratory illness as well as by RSV tests conducted during routine clinical care.
Event rates were modeled as a function of chronologic age and birth month, and the researchers calculated overall rates and rates for infants with and without exposure to young siblings or daycare.
Among the 1,642 infants that met evaluation criteria, rates of outpatient RSV LRI increased at older ages. In contrast, rates of RSV hospitalization were significantly higher among the youngest infants. Among all infants, the incidence of RSV hospitalization decreased from 8.2 (95% CI, 6.9-9.7) per 100 infant-seasons among infants aged younger than 1 month to 2.3 (95% CI, 1.8-2.9) per 100 infant-seasons among infants aged 10 months.
For preterm infants aged younger than 1 month who were exposed to other young children, the RSV hospitalization rates rose to 13.8 (95% CI, 11.5-16.6) per 100 infant-seasons.
Similarly, rates of RSV ICU admission were highest among the youngest infants, ranging from 3.1 (95% CI, 2.7-3.6) per 100 infant-seasons among infants aged younger than 1 month to 0 per 100 infant-seasons among infants aged 10 months.
The highest RSV hospitalization and ICU admission rates occurred among infants born in February and who were exposed to young children — at 19 (95% CI, 13.5-27) and 7.9 (95% CI, 5.7-11), respectively.
Additionally, Simões and colleagues argued that their research refutes claims that the risk for RSV hospitalization among infants born preterm is similar to that of infants born full-term. They estimated that the rate of RSV hospitalization among infants aged younger than 1 month born at 32 to 35 weeks gestational age was 82 (95% CI, 69-97) per 1,000 infant-seasons. This rate is significantly higher than those estimated for infants of all gestational ages, which peak in the second month of life at 25.9 (95% CI, 21.3-30.8) per 1,000 infant-seasons.
“These data demonstrate that higher risk for 32 to 35 [weeks gestational age] infants can be easily identified by age or birth month and significant exposure to other young children. These infants would benefit from targeted efforts to prevent severe RSV disease,” they wrote. – by Sarah Kennedy
Disclosure: The study was sponsored by AstraZeneca, the parent company of MedImmune. Some authors are or have been employed by AstraZeneca and MedImmune.