Appropriateness of Age Thresholds for Respiratory Syncytial Virus Immunoprophylaxis in Moderate-Preterm Infants

Abstract

IMPORTANCE Recommendations concerning the appropriate age threshold for respiratory syncytial virus (RSV) prophylaxis in moderate-preterm infants are highly debated. OBJECTIVE To determine the age at which moderate-preterm infants' risk of RSV hospitalization has decreased to the risk observed in low-risk term infants. DESIGN, SETTING, AND PARTICIPANTS Retrospective cohort study of Florida and Texas Medicaid fee-for-service billing records matched to birth certificates from Medicaid beneficiaries aged 0 to 12 months with a sibling younger than 5 years and without other indications for RSV prophylaxis between January 1, 1999, and December 31, 2004. EXPOSURES For each state, we used discrete time survival analysis to develop age trend models for RSV hospitalizations for 2 groups: moderate-preterm infants (32-34 weeks' gestational age) and term infants (37-41 weeks' gestational age). MAIN OUTCOMES AND MEASURES Age at which preterm infants' risk of RSV hospitalization equaled the risk for term infants at age 1 month. RESULTS Our cohort included 247,566 eligible infants with 5322 RSV hospitalizations. Preterm status doubled the risk for RSV hospitalization in both Florida (odds ratio = 2.41; 95% CI, 1.85-3.12) and Texas (odds ratio = 1.94; 95% CI, 1.64-2.30). Preterm infants' risk of RSV hospitalization was similar to that for 1-month-old term infants at ages 4.2 months (95% CI, 2.5-5.7) in Florida and 4.5 months (95% CI, 2.8-6.4) in Texas. CONCLUSIONS AND RELEVANCE The age at which moderate-preterm infants showed RSV hospitalization risk similar to their healthy term counterparts supports the more restrictive age thresholds in RSV immunoprophylaxis recommendations. Further studies are warranted to investigate the age-dependent risk of RSV hospitalization in other RSV risk groups.

Updated Guidance for Palivizumab Prophylaxis Among Infants and Young Children at Increased Risk of Hospitalization for Respiratory Syncytial Virus Infection

“…In recent large cohort studies of moderately preterm infants, the majority of whom did not receive palivizumab, 2.5% to 4.9% required hospitalization for RSV infection during the RSV season indicating that more than 95% did not require hospitalization. 40 The rate of hospitalization among infants ≥35 weeks' gestation (5.1/1000) was no different than the rate for term infants (5.3/1000; Table 1). The hospitalization rate of infants ≥30 weeks to 35 weeks' gestation indicate only a slight increase in risk (less than twofold; Tables 1, 2, and 3).…”

“…39 The RSV hospitalization rate increased with decreasing gestational age, with a breakpoint at ≤28 weeks' gestation ( 40 Choosing an appropriate cutoff for gestational age for which palivizumab prophylaxis may be considered for preterm infants without other indications is challenging. Data consistently demonstrate the greatest increase in risk for hospitalization is in preterm infants born before 29 weeks' gestation.…”

“…34,35,38 Most of these hospitalizations occur in the first 90 days after birth. 22,34,40 Certain subgroups of infants with comorbidities such as prematurity, CLD, or hemodynamically significant CHD have increased risks for RSV hospitalization, although the degree of risk varies among studies. 30,78 The risk of RSV hospitalization associated with most other risk factors has been difficult to determine because of low rates of occurrence.…”

Respiratory Syncytial Virus–Associated Mortality in Hospitalized Infants and Young Children

“…In a recent study, ,1% of the Medicaid birth cohorts in Florida and Texas received palivizumab. 27 In another multicenter study, only 9% of hospitalized children had ever received palivizumab. 2 Finally, infants who receive palivizumab are generally those with prematurity or CCC, conditions that may also predispose them to death.…”

Authors’ Responses In Response to the Letter From Ambrose

“…Surprisingly, Ambrose suggests greater use of palivizumab prophylaxis is justified by quoting Winterstein et al 4 This publication evaluated the age at which moderate preterm Medicaid-enrolled infants without other indications for RSV prophylaxis showed an RSV hospitalization risk similar to that of healthy term infants in Florida and Texas. Although moderately premature infants show about twice the risk of RSV hospitalization during the first month of life, this risk drops to no recognizable differences at an age of 4 months.…”