National Prevalence and Risk Factors of Hepatitis B Virus Infection in Tunisia Two Decades After Vaccine Introduction

Background/Objectives: Tunisia lacks recent national data on hepatitis B virus (HBV) prevalence, particularly following the introduction of universal HBV vaccination in 1995. A national HBV seroprevalence study is essential to guide prevention strategies. This study aimed to estimate the national seroprevalence of HBV infection and identify its determinants 20 years after vaccine introduction. Methods: We conducted a nationwide, household-based, cross-sectional sero-epidemiological survey among a representative sample of the Tunisian general population using a two-stage cluster sampling method. The study was conducted by the National Observatory of New and Emerging Diseases (ONMNE) between December 2014 and June 2015. Data were collected using standardized questionnaires, and blood samples were tested using electrochemiluminescence (ECLIA) to detect HBV biomarkers (HBsAg, anti-HBc, anti-HBs). HBV infection was defined as the presence of HBsAg and/or anti-HBc with the absence of anti-HBs. Associations between HBV infection and explanatory variables (socio-demographics, vaccination status, intrafamilial transmission, and hospital exposures) were assessed using multivariate logistic regression, reporting adjusted odds ratios (aORs) with 95% confidence intervals (CIs). Results: Among 21,720 participants, 19,155 (88.2%) were tested. The national prevalence of HBsAg was 1.7% (95% CI: 1.55-1.85%), higher among males (2.1%; 95% CI: 1.9-2.4%) than females (1.4%; 95% CI: 1.3-1.6%) (p < 0.001; M/F ratio = 1.48). The mean age of HBsAg-positive participants was 48 ± 15.7 years. Prevalence was highest in the Central (2.3%; 95% CI: 2.0-2.7%) and Southern regions (2.2%; 95% CI: 1.8-2.8%) (p < 0.001). In multivariate analysis, independent risk factors for HBV infection included age >20 years (aOR = 15.10; 95% CI: 4.79-47.64; p < 0.001), having a family member with HBV infection (aOR = 2.82; 95% CI: 2.09-3.79; p < 0.001), residing in the Southern (aOR = 2.51; 95% CI: 1.76-2.71; p < 0.001) or Central region (aOR = 2.18; 95% CI: 1.76-2.71; p < 0.001), male gender (aOR = 1.69; 95% CI: 1.39-2.05; p < 0.001), and hospital follow-up (aOR = 1.23; 95% CI: 1.01-1.51; p = 0.039). HBV vaccination was strongly protective (aOR = 0.36; 95% CI: 0.20-0.62; p < 0.001). Conclusions: The national HBsAg seroprevalence in Tunisia was 1.7%, reflecting a low-endemic status. Vaccination programs should prioritize high-risk groups, including males, adults over 20 years, household contacts of HBV carriers, and residents of the Central and Southern regions. Strengthening infection prevention and control in healthcare settings and adopting intrafamilial precautions among high-risk populations are essential for long-term HBV control.