To identify predictors of WNV-IgG seropositivity, examine the relationship between WNV-IgG and neutralizing antibody titers, identify predictors of neutralizing responses, and characterize antibody kinetics over approximately four years.
Approach:
Study Design: Cross-sectional surveillance of health care workers (HCWs) at Sheba Medical Center in Israel, supplemented by a retrospective longitudinal analysis using archived samples collected from 2020 to 2024.
Data Collection: Participants completed a medical background questionnaire and provided serum for WNV-IgG testing. Seropositive participants underwent neutralization testing; archived samples were available for a longitudinal subgroup.
Statistical Analysis: Multivariable logistic and linear regression models assessed predictors of seropositivity and neutralizing responses. Linear mixed-effects models estimated antibody waning.
Key Findings:
WNV-IgG was detected in 14.8% of the 2,032 HCWs included in the final analysis.
Detectable neutralizing antibodies were found in 94.0% of WNV-IgG–seropositive participants.
Older age independently predicted IgG seropositivity.
Neutralizing titers declined by approximately 23% annually over as long as 44 months but generally remained high.
Interpretation:
WNV-IgG seropositivity increased with age, consistent with cumulative exposure. Most seropositive HCWs had detectable neutralizing activity, although IgG levels explained only part of the variability in neutralization.
Limitations:
Participants were HCWs from a single region, limiting generalizability.
Infection timing was unknown, limiting estimates of antibody persistence.
Incomplete yellow fever and Japanese encephalitis vaccination histories introduced possible antibody cross-reactivity.
Conclusion:
Asymptomatic WNV exposure was associated with durable neutralizing responses despite gradual antibody waning. The findings characterize naturally acquired humoral immunity but do not establish the duration of clinical protection.
