Hepatitis B Seroprevalence among Petrochemical Workers: Workplace Versus Community Baseline in Nigeria

Abstract

Objectives: Hepatitis B virus (HBV) remains hyperendemic in Nigeria, with national HBsAg seroprevalence estimated at 8.1% among adults aged 15–64 years. Petrochemical workers face occupational blood-exposure risks through industrial injuries, yet facility-specific baseline data are scarce. This study aimed to establish facility-specific baseline seroprevalence among petrochemical workers, test the validity of community-extrapolation assumptions in occupational health policy, and examine plausible mechanisms for any observed divergence between workplace and community rates. Methods: We conducted a cross-sectional screening of 184 consecutive petrochemical workers undergoing mandatory periodic fitness-to-work evaluation at three operational locations in Nigeria between November 2018 and April 2019. HBsAg was detected using a rapid immunochromatographic assay (sensitivity ≥99.0%, specificity ≥99.0%). Prevalence was calculated with exact binomial 95% confidence intervals. Prevalence ratios and approximate 95% CIs were computed using the delta method on the log scale against community baselines. Fisher exact test was used for categorical associations. Results: The cohort comprised 178 males (96.7%) and 6 females (3.3%), with mean age 43.9 ± 5.4 years. One worker tested HBsAg-positive, yielding a prevalence of 0.54% (exact 95% CI: 0.01–2.99%). Compared with the Nigeria NAIIS 2018 baseline, the prevalence ratio was 0.07 (95% CI: 0.01–0.43), p < 0.001. Compared with the pooled Nigerian meta-analytic estimate, the prevalence ratio was 0.06 (95% CI: 0.01–0.40), p < 0.001. Neither community baseline confidence interval overlapped with the workplace estimate. Sensitivity analysis confirmed robustness: even with five positive cases, prevalence remained below the national lower bound. Conclusions: A 0.54% seroprevalence—approximately 15-fold below the national baseline—demands mechanistic explanation rather than celebration. Pre-employment screening, vaccination coverage, and workforce selection effects are plausible, non-mutually-exclusive drivers. Facility-specific seroprevalence monitoring, vaccination audits, and hiring-screening transparency are required before low workplace rates can be interpreted as prevention success.