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Preterm infants have higher risk for RSV
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Preterm infants who did not receive respiratory syncytial virus prophylaxis were three times more likely to be hospitalized for RSV than infants of the general population. Additional risk factors for RSV infection included daycare attendance or having siblings who attended daycare, according to study findings in The Pediatric Infectious Disease Journal.
Christopher S. Ambrose, MD, of MedImmune Medical and Scientific Affairs, and colleagues followed preterm infants with a gestational age of 32 to 35 weeks during two RSV seasons (defined as September through May) in 2009-2010 (n=407) and 2010-2011 (n=1, 239). Study participants were aged younger than 6 months as of Nov. 1 in each study period and were excluded if they received or were scheduled to receive RSV prophylaxis. Nasal and pharyngeal swabs were collected if study participants presented to outpatient care for acute respiratory illness. The study was conducted at 188 outpatient clinics in 38 US states.
Christopher S. Ambrose
Overall, 1, 032 infants developed 3, 023 episodes of acute respiratory illness. Of these, 72% (n=2,163) had samples collected for RSV testing. RSV was confirmed in 287 infants.
Disease rates were 25.4 per 100 infant-seasons for any RSV acute respiratory illness; 9.3 per 100 infant-seasons for RSV-related upper respiratory tract illness; 13.7 per 100 infant-seasons for RSV-related lower respiratory tract illness; 5.9 per 100 infant-seasons for RSV ED visits; and 4.9 per 100 infant-seasons for RSV hospitalization.
Daycare attendance and preschool-aged, non-multiple birth siblings were consistent risk factors for RSV.
When controlling for other factors, chronologic age of younger than 3 months was associated with lower risk for RSV-related acute respiratory illness among infants with a gestational age of 32 to 34 weeks. This population’s risk for RSV hospitalization did not change through 6 months.
Among infants with a gestational age of 35 weeks, chronologic age of younger than 3 months was associated with a higher risk for RSV hospitalization. RSV hospitalization rates among these infants, aged younger than 3 months, or 3 to 6 months, were similar to rates among infants with a gestational age of 32 to 34 weeks.
The population with the highest risk for RSV hospitalization between November and March were infants with a gestational age of 32 to 34 weeks based on the 2012 AAP risk factors. The RSV hospitalization rate among this population was 9.2 per 100 infant-seasons, compared with 3.5 per 100 infant-seasons among all other study participants. Infants with 2012 AAP risk factors while aged younger than 6 months accounted for 75% of RSV ICU admissions.
The study findings are significant, according to the study authors, because current AAP recommendations regarding RSV prophylaxis exclude preterm infants with a gestational age of 32 to 35 weeks. The risk for RSV is often not considered important enough to warrant the cost of prophylaxis. RSV prophylaxis is not recommended for otherwise healthy infants with a gestational age of 35 weeks, and is only recommended for infants with a gestational age of 32 to 34 weeks who have one of two AAP risk factors, according to researchers.
"These results indicate that the 2012 AAP environmental risk factors can identify the infants with a gestational age of 32 to 35 weeks with an elevated risk for severe RSV disease," they said.
Eric A. Simões
“The significant burden of RSV disease observed in this study highlights the risk of RSV hospitalization facing infants born between 32 and 35 weeks gestational age. What’s more insightful, however, are the findings that indicate a high risk for RSV-related hospitalization among certain sub-groups of infants within this population,” study researcher Eric A. Simões, MBBS, DCH, MD, of the University of Colorado, in Aurora, Colo., said in a press release.
Disclosure: See the study for a full list of disclosures.
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