Vaccines and antivirals against respiratory syncytial virus (RSV) are being developed, but there are scarce data on the full impact of RSV infection on outpatient children.

We analyzed the burden of RSV illness in a prospective cohort study of children aged ≤13 years during 2 consecutive respiratory seasons in Turku, Finland (2231 child-seasons of follow-up). We examined the children and obtained nasal swabs for the detection of RSV during each respiratory illness. The parents filled out daily symptom diaries throughout the study.

Of 6001 medically attended respiratory infections, 302 (5%) were caused by RSV. Per 1000 children, the average annual RSV infection incidence rates among children aged <3, 3–6, and 7–13 years were 275, 117, and 46 cases, respectively. In children aged <3 years, acute otitis media developed in 58%, and 66% of children in this age group received antibiotics. The mean duration of RSV illness was longest (13.0 days) and the rate of parental work absenteeism was highest (136 days per 100 children with RSV illness) in children aged <3 years.

The burden of RSV is particularly great among outpatient children aged <3 years. Young children are an important target group for the development of RSV vaccines and antivirals.