Association of Age With Risk of Hospitalization for Respiratory Syncytial Virus in Preterm Infants With Chronic Lung Disease

IMPORTANCE It is unknown whether the age threshold (<= 24 months) for preterm infants with chronic lung disease (CLD) to receive immunoprophylaxis for respiratory syncytial virus (RSV) as currently recommended by American Academy of Pediatrics guidelines correctly identified infants at higher risk for hospitalization for RSV. OBJECTIVE To determine the age when the risk of hospitalization for RSV among preterm infants with CLD becomes equivalent to the risk for healthy, 1-month-old term infants who do not qualify for immunoprophylaxis. DESIGN, SETTING, AND PARTICIPANTS A retrospective cohort study was conducted of 1 018 593 healthy term infants and 5181 preterm infants with CLD using Medicaid billing records (Medicaid Analytic eXtract files) from January 1, 1999, to December 31, 2010, linked to Florida and Texas birth and death certificates. EXPOSURES Age-trend discrete time logistic regression models within a survival analysis framework were developed, adjusting for covariates including the use of immunoprophylaxis, to compare the risk of hospitalization of preterm infants (<32 weeks' gestational age) with CLD at 3 through 34 months of age with the risk of hospitalization of term infants (37-41 weeks' gestational age) at 1 month of age. MAIN OUTCOMES AND MEASURES Age at which risk of hospitalization for RSV among preterm infants with CLD equals the risk for healthy term infants at age 1 month. RESULTS The study cohort included 1 018 593 healthy term infants and 5181 preterm infants with CLD; because patients could reenter the cohort for a second or third season, the total study cohort consisted of 1 880 531 healthy term infant-seasons (926 206 girls and 954 325 boys; mean [SD] age at first season entry, 12.6 [9.6] months) and 8680 CLD infant-seasons (3519 girls and 5161 boys; mean [SD] age at first season entry, 15.1 [9.1] months). Among term infants with siblings, the risk of hospitalization for RSV averaged across all covariate strata was 9.0 (95% CI, 8.4-9.6) per 1000 patient season-months at 1 month of age. The risk of hospitalization for RSV among preterm infants with CLD became similar to that of 1-month-old term infants at an age of 18.5 months (95% CI, 15.6-22.8). CONCLUSIONS AND RELEVANCE The age threshold at which the risk of hospitalization for RSV among qualifying preterm infants with CLD approximates that of healthy term infants supports the current American Academy of Pediatrics practice guideline recommending RSV prophylaxis until a maximum of 24 months of age.