Prevalence and factors associated with hepatitis B surface antibody seroprotection among healthcare workers undergoing laboratory testing at Eastgate Clinic, Windhoek, Namibia: A retrospective cross-sectional study

Healthcare workers are occupationally exposed to blood and body fluids and require effective protection against hepatitis B virus infection. Evidence on hepatitis B surface antibody (anti-HBs) seroprotection among healthcare workers in Namibia remains limited. We estimated the prevalence of anti-HBs seroprotection and examined associated factors among healthcare workers tested at Eastgate Clinic in Windhoek, Namibia. We conducted a cross-sectional analysis of routinely collected anti-HBs test records from 1 January to 31 December 2025. The first chronological test per individual was included. Anti-HBs concentrations [≥]10 mIU/mL were classified as seroprotective. Results outside the assay reporting range were treated as censored but remained classifiable for the binary outcome. Prevalence estimates were reported with Wilson 95% confidence intervals (CIs). Modified Poisson regression with robust standard errors was used to estimate adjusted prevalence ratios (aPRs). The register contained 304 test records representing 299 unique individuals. After excluding three individuals with missing anti-HBs results, 296 were analysed; 163 (55.1%) were female. Overall, 148 individuals were seroprotected, corresponding to a prevalence of 50.0% (95% CI 44.3-55.7%). Seroprotection was lowest among participants aged 18-29 years (35.3%) and highest among those aged 50-59 years (71.1%). Each 10-year increase in age was associated with a higher prevalence of seroprotection after adjustment for sex (aPR 1.14, 95% CI 1.06-1.24; p=0.001), whereas sex was not independently associated with seroprotection (aPR 0.97, 95% CI 0.78-1.22; p=0.797). The age association remained consistent across sensitivity analyses. Half of the healthcare workers tested had anti-HBs concentrations below the operational seroprotection threshold. These findings support systematic vaccination verification, appropriately timed post-vaccination testing, and documented follow-up of non-protective results. The absence of vaccination history, occupational characteristics, testing indications, and additional hepatitis B serological markers limited causal and clinical interpretation.