Factors associated with respiratory syncytial virus-neutralizing antibody titers in adults.

BACKGROUND

Respiratory syncytial virus (RSV) is associated with high morbidity in children. Despite recent advances in vaccine development for adults and maternal vaccination strategies to protect newborns, data on RSV seroprevalence and neutralizing antibody titers in adults remain limited. This study aimed to measure RSV-neutralizing antibody titers in adults and explore associated background characteristics.

METHODS

This cross-sectional study was conducted from July 10 to July 18, 2024, among healthcare and non-healthcare workers at a pediatric medical facility in Japan. Blood samples collected during routine health checkups were analyzed for RSV-neutralizing antibody titers. Multivariable modified Poisson regression was used to examine associations between antibody titers and background characteristics collected using a structured questionnaire. A restricted cubic spline model was applied to assess age-related trends in antibody titers.

RESULTS

Among 1226 participants, 4.5 % were seronegative and 63.5 % had RSV-neutralizing antibody titers ≥8-fold. The spline model showed that titers were highest in the early 20s, declined in the 30s, modestly increased in the early 40s, and declined thereafter. Higher titers (≥8-fold) were associated with age 30-39 years (prevalence ratio [PR], 0.85; 95 % confidence interval [CI], 0.74-0.97), presence of chronic disease (PR, 1.11; 95 %CI, 1.01-1.22), and having children <9 years in the household (PR, 1.17; 95 %CI, 1.03-1.33).

CONCLUSIONS

RSV-neutralizing antibody titers showed age-dependent variation, with notably lower levels among individuals in their 30s. Higher titers were associated with chronic conditions and living with younger children, highlighting the role of exposure history in shaping immunity.