Respiratory Syncytial Virus (RSV) Hospital Admission Rates and Patients' Characteristics Before the Age of Two in England, 2015-2019

BackgroundA granular understanding of respiratory syncytial virus (RSV) burden in England is needed to prepare for new RSV prevention strategies. We estimated the rates of RSV hospital admissions in infants before age two in England and describe baseline characteristics. MethodsA birth cohort of all infants born between 01/03/2015 and 28/02/2017 (n=449,591) was established using Clinical Practice Research Datalink-Hospital Episode Statistics. Case cohorts included infants with an admission for 1) RSV-coded, 2) bronchiolitis-coded, 3) any respiratory tract infection (RTI)-coded <24 months and 4) RSV-predicted by an algorithm <12 months. Baseline characteristics were described in case and comparative cohorts (infants without corresponding admission). Cumulative incidence and admission rates were calculated. Multiple linear regression was used to estimate the proportion of RTI healthcare visits attributable to RSV. ResultsThe RSV-coded/RSV-predicted case cohorts were composed of 4,813/12,694 infants (cumulative incidence: 1.1%/2.8%). Case cohort infants were more likely to have low birth weight, comorbidities and to be born during RSV season than comparative cohort infants, yet >77% were term healthy infants and >54% born before the RSV season. During the first year of life, 11.6 RSV-coded and 34.4 RSV-predicted hospitalizations occurred per 1,000 person-years. Overall, >25% of unspecified lower RTI admissions were estimated to be due to RSV. ConclusionsIn England, one in 91 infants had an RSV-coded admission, likely underestimated by [~]3-fold. Most infants were term healthy infants born before the RSV season. To decrease the total burden of RSV at the population level, immunization programs need to protect all infants.