Burden of Respiratory Syncytial Virus (RSV) in Children in Sweden (BRICS): A Retrospective Study in Sweden

Primary Objective: -Estimate the hospital-associated healthcare resource use (HCRU), and associated costs, of RSV infection in children in comparison to the non-RSV control cohort (general population) and patients with rhinovirus infection. Secondary Objectives: * Describe demographic and clinical patient characteristics of RSV infected children. * Estimate and compare the incidence of RSV infection and acute respiratory infections (ARIs) in children. * Estimate the mortality associated with RSV infection in children. * Estimate the social economic burden of RSV infection in children in relation to parents staying home from work to care for their sick child (VAB leave) in comparison to non-RSV control cohort (i.e. parents to children in the general population). * Estimate the net days with VAB leave and the compensation disbursed (temporary parental benefit) associated with RSV infection in children. * Estimate the indirect costs that can be attributed to VAB leave. * Examine the medium- and long-term complications associated with an RSV diagnosis in children in comparison to the non-RSV control chart (general population) and patients with rhinovirus infection. * Examine and describe risk factors associated with an RSV infection in children * Estimate the healthcare resource use (HCRU), and associated costs, of RSV infection in children, for a subset of patients where primary care data is available, in comparison to the non-RSV control cohort (general population).

The overall study period will be between July 1st 2001 and to latest available date (likely June 30th 2022). Patients will be identified for inclusion in the study population between July 1st 2006 and June 30th 2021. Patients will be followed from time of inclusion until end of the study period or until death. All patients will have an index date corresponding to the date of diagnosis of incident infection in primary and/or hospital care during the identification period. An incident infection is defined as the occurrence of infections more than 30 (\>30) days apart. This implies that a patient can have more than one index date during the study period. Patients that are included in both the RSV cohort and the regional primary care RSV cohort may have two different index dates for the same incident infection, depending on the objective. This is if a patient is first treated in primary care and then hospitalized. The index date is defined differently for the two cohorts, as the first diagnosis in hospital care for the RSV cohort and first diagnosis in primary care OR hospital care for the regional primary care cohort. The non-RSV controls will have the same index date as their matched RSV patient. The look-back period will be used to inform baseline characteristics as well as patients' medical and diagnosis history. All patients will have possible look-back from birth for information on the patient's hospital care history and from 2005 for information on the patient's prescribed drugs history. The individual look-back and follow-up will depend on the time of inclusion in the study population as well as age at inclusion.