Trends and patterns of varicella zoster virus infection in Kilifi: A population-based serosurvey

There is limited epidemiologic data on varicella zoster virus (VZV) infections from low- and middle-income countries including Kenya. We aimed to describe the seroepidemiology of VZV in Kilifi, Kenya, where varicella vaccine is not included in the national infant immunization program, in order to generate evidence to inform vaccine policy. We conducted a retrospective serosurvey utilizing archived plasma and serum samples from cross-sectional population-based serosurveys conducted within the Kilifi Health and Demographic Surveillance System between 2009 and 2021. We assayed immunoglobulin G (IgG) for VZV using a validated Luminex multiplex immunoassay and applied a seropositivity cutoff of ≥0.26 International Units per millilitre (IU/mL), as determined by the assay developer. We calculated Bayesian-adjusted age-specific seroprevalence and tested differences in seroprevalence between groups using Chi square. We used a multivariable logistic regression model to estimate associations with VZV IgG antibody seropositivity. We fitted an age-dependent catalytic model to estimate the force of infection (FOI) in children aged 0.5-4, 5-9 and 10-14 years. A total of 2639 samples from children aged