Disparities in RSV Hospitalisations Among Children Under 2 Years in NSW , Australia

AIM: To estimate RSV hospitalisation rates among children ≤ 2 years in New South Wales (NSW), Australia over two decades; to examine how rates varied by age, prematurity and selected co-morbidities and to describe temporal, seasonal and geographic patterns in RSV hospitalisation across NSW. METHODS: RSV hospitalisation rates were calculated using linked population data for all children ≤ 2 years in NSW from 2002 to 2020 (n = 1 770 628). Infant and maternal factors were analysed as covariates using a univariate log-binomial model to determine RSV admission risk between groups. Geographical distributions were visualised using heatmaps according to location at birth. RESULTS: The overall RSV hospitalisation rate during 2004-2020 was 11.2 per 1000 child-years (95% CI 11.1-11.4) while during the contemporary pre-pandemic period of 2016-2019, the rate was 15.4 (15.1-15.7). Compared to children born term without comorbidities (8.41 admissions per child-years at risk [7.96-8.88]), rates of RSV hospitalisations were significantly higher among premature children (23.8 [23.2-24.5]) and children with any co-morbidities (48.2 [46.1-50.4]). Children with primary immunodeficiency (8.12 [6.78-9.72]), bronchopulmonary dysplasia (6.54 [6.06-7.06]), Down syndrome (5.10 [4.38-5.93]) and congenital heart disease (3.70 [3.53-3.88]) had persistently elevated hospitalisation rates into the second year of life. Hospitalisation rates were higher in Greater Sydney and subtropical northeastern coastal NSW where RSV activity began earlier and was less seasonally defined than temperate regions. CONCLUSIONS: Strategies to protect premature children and those with comorbidities against RSV are warranted up to 2 years of age given the persistently elevated RSV risk. Regional RSV epidemiology should be considered when developing immunisation strategies.