Preterm birth and the risk of infant respiratory syncytial virus associated acute lower respiratory infection in Australia's Northern Territory

ObjectiveThe Northern Territory (NT) of Australia has high rates of both preterm birth and childhood respiratory syncytial virus (RSV) infections. This study evaluated preterm birth and subsequent risk of RSV-associated acute lower respiratory infection hospital admission (RSV-ARLI) among NT infants during their first year of life. MethodsA retrospective, population-based cohort study of NT mother-infant pairs from 2008 to 2017. Preterm birth was defined as gestation <37 weeks. RSV-ALRI hospitalisations were identified using ICD-10-AM codes (J12.1, J20.5, J21.0, or J09-J22 plus B97.4). Risk of RSV-ALRI in preterm infants was assessed using generalised linear regression to calculate risk ratios (RR). Two multivariable models were used: one including all covariates (aRR1) and another with stepwise elimination retaining only significant factors (aRR2). ResultsOverall, 10% (3839/39148) of infants were born preterm and 2% (846/39148) were hospitalised with RSV-ALRI. Preterm infants (4%) had a significantly higher risk or RSV-ALRI than term infants (2%) (risk ratio [RR] 2.26, 95% CI 1.90-2.69). This persisted even after adjustment for demographic, antenatal and infant health characteristics (aRR1 1.72, 1.43-2.08; aRR2 1.83, 95% CI 1.52-2.19). The risk of RSV-ALRI was highest among infants born <31 weeks gestation (7%). First Nations infants (4%) and those from very remote central desert regions (7%) also had a high risk of RSV-ALRI hospitalisation. ConclusionPreterm birth is a common and significant risk factor for infant RSV hospitalisation in Australias NT. RSV immunisation strategies will be crucial in protecting high-risk infants in the region. Article SummaryPreterm birth doubles RSV hospitalisation risk in Australias Northern Territory. First Nations children and those in remote regions experienced the highest RSV burden. Whats Known on This SubjectPreterm birth and acute respiratory infections contribute substantially to infant morbidity in Australias Northern Territory. Globally, respiratory syncytial virus is a leading cause of hospitalisation, and preterm infants account for a disproportionate share of RSV-associated admissions in early childhood. What This Study AddsThis is the first population-based study quantifying the RSV hospitalisation risk among preterm infants in northern Australia. Preterm birth significantly increases RSV hospitalisation risk. First Nations children and remote populations were identified as priority prevention targets.