Few population-based studies have evaluated the importance of pre-existing respiratory syncytial virus (RSV) antibody on RSV susceptibility among children and adults. We conducted a prospective, community-based cohort study among individuals aged 6 months-50 years in Oregon and Washington State, USA (June 2022-May 2023), with weekly symptom surveys and swab collection regardless of symptoms. Swabs were tested for RSV using RT-qPCR. Enrollment sera were tested for RSV prefusion F IgG binding (all participants) and neutralizing antibodies (pediatric participants). We detected 305 RSV illnesses among 3237 participants from 1188 households. Using proportional hazards regression, higher RSV binding antibody titers were associated with a lower estimated hazard of RSV among pediatric participants (hazard ratio=0.66 per 1-unit difference in log10-RSV antibody titer; 95% CI: 0.56, 0.78). In a post-pandemic period, pre-existing RSV antibody titers were associated with a lower risk of RSV illness in children aged 6 months-17 years, which could inform vaccine development for this age group. This study found higher RSV antibody levels were associated with lower RSV risk in children outside the hospital. An earlier rise in incidence and higher incidence rates were observed among children <5 years compared to older children and adults.
Frivold et al. (Fri,) studied this question.