Evaluation of hepatitis B vaccine effectiveness among fully vaccinated healthcare workers in Ethiopia

Hepatitis B vaccination is administered for Healthcare workers (HCWs) in three doses at 0, 1, and 6 months to provide immunity. However, in the study area, the effectiveness of the HBV vaccine remains uncertain. This study aimed to evaluate the effectiveness of the hepatitis B vaccine and identify factors influencing its effectiveness among fully vaccinated HCWs in all hospitals within East Gojjam Zone, Northwest Ethiopia. A hospital-based cross-sectional study was conducted among 422 HCWs from March to November 2024. Simple random sampling technique was used to recruit the study participants. Total sample size was allocated proportionally to each hospital. Five to seven milliliters of venous blood samples were collected and serum samples were analyzed to detect the anti-hepatitis B surface antigen (anti-HBs), hepatitis B surface antigen (HBsAg), and anti-hepatitis B core antibody (anti-HBc) using a sandwich enzyme-linked immunosorbent assay (ELISA). Data were analyzed using SPSS software version 25. Of fully vaccinated HCWs, 346/422 (82.0%) (95% CI: 78.0–86.0%) of them were sero-protected (had anti-HBs titer ≥ 10 mIU/ml). The concentration of protective anti-HBs (≥ 10 mIU/mL) was observed in 337/401 (84.0%) of non-smokers. The overall sero-positivity of HBsAg was 23/422 (5.5%) (95% CI: 3.0–8.0). Blood transfusion (AOR: 16.5, 95% CI: 1.53, 29.24) (P < 0.011) and dental extraction (AOR: 13.5, 95% CI: 3.99, 45.57) (P < 0.000) were significantly associated with HBsAg positivity. Moreover, the paradoxical co-existence of HBsAg and anti-HBs was 4.6% (95% CI: 2.0–7.0%). In addition, the overall sero-positivity of anti-HBc was 30/422 (7.1%) (95% CI: 5.0–10.0). Injectable medication (AOR: 4.3, 95% CI: 1.73, 10.72) (P < 0.002) was significant determinant for anti-HBc sero-positivity. The study revealed suboptimal hepatitis B vaccine effectiveness, leading to intermediate HBV infection rates in the study area. These findings highlight the importance of monitoring post-vaccination anti-HBs antibody levels to address gaps in protection.