Occult hepatitis B virus infection among hepatitis B surface antigen negative vaccinated healthcare workers in East Gojjam zone hospitals

Occult hepatitis B infection (OBI) is defined as the presence of hepatitis B virus (HBV) DNA in the serum of individuals who test negative for hepatitis B surface antigen (HBsAg). OBI poses a significant public health challenge, especially in hyperendemic regions like Ethiopia, where it can persist even among vaccinated populations. The phenomenon is of particular concern among healthcare workers, who are at increased risk of HBV infection. This study aimed to determine OBI and its associated factors among fully vaccinated, hepatitis B surface antigen (HBsAg)-negative healthcare workers in hospitals of East Gojjam Zone, Northwest Ethiopia. An institution-based cross-sectional study was conducted from March 25 to November 30, 2024 among 399 fully vaccinated healthcare workers in eleven hospitals in East Gojjam Zone. Socio-demographic and clinical data were collected using a self-administered questionnaire. Five up to seven milliliters of venous blood were collected from each study participant and 100 µL serum samples was used to screen HBsAg via enzyme-linked immunosorbent assay (ELISA), and HBsAg-negative samples underwent HBV DNA detection and quantification using the Abbott real-time polymerase chain reaction (PCR). Data were analyzed using SPSS version 25 and crude prevalence ratio (CPR) and adjusted prevalence ratio (APR) were calculated at 95% confidence intervals. Statistical significance was set at p < 0.05. Of the 399 fully vaccinated, HBsAg-negative healthcare workers, 39 (9.8%; 95% CI: 7.0-13.0%) were found to have detectable HBV DNA, confirming OBI. Among these, 31/39 (79.5%) had low-level viremia (< 200 IU/mL), while 8/39 (20.5%) had higher viral loads (> 200 IU/mL). Alcohol use (APR: 2.5, 95% CI: 2.1 to 7.2, p < 0.021) and multiple sexual contacts (APR: 3.7, 95% CI: 2.8 to 6.4, p < 0.003) were independent risk factors for OBI. Despite full vaccination, a significant number of healthcare workers in this study were found to have OBI. This highlights the limitations of relying only on HBsAg screening for HBV detection.