Incidence and risk factors of hospitalisations for respiratory syncytial virus among children aged less than 2 years

The study aim was to examine the incidence and risk factors of respiratory syncytial virus (RSV) bronchiolitis hospitalisations and disease severity among infants. We compared demographic and health characteristics of children aged 0-23 hospitalised for RSV bronchiolitis (cases, n = 1227) during 2008-2018 and control children (n = 554) of the same age admitted for non-respiratory disease. RSV antigen was detected in nasal swabs by immunochromatography. Multiple logistic regression models were applied. The average annual incidence of hospitalisation for RSV bronchiolitis was 12.6 per 1000 and 1.7 per 1000 (P < 0.001) among infants and toddlers, respectively, with winter seasonality (November-March). The risk of hospitalisation for RSV bronchiolitis increased among children aged 0-5 months (OR 7.66; 95% CI 5.61-10.45) and 6-11 months (OR 12.88, 95% CI 8.48-19.55), compared to those aged 12-23 months. Additional risk factors were living in low vs. higher socio-economic status towns (OR 1.49; 95% CI 1.14-1.95), having chronic medical conditions (OR 2.75; 95% CI 1.61-4.70), birth month (October-January vs. June-September) (OR 2.19; 95% CI 1.60-2.99) and history of stay in neonatal intensive care unit at birth (OR 2.37; 95% CI 1.27-4.41). Male children and those who had pneumonia were more likely to have severe RSV bronchiolitis. In conclusion, the burden of hospitalisations for RSV bronchiolitis is high, especially in young infants. Effective preventive measures such as RSV active vaccines can reduce the risk of hospitalisations for RSV bronchiolitis among these vulnerable groups.