The length of protection after a first round of hepatitis B vaccination in children and adolescents is unknown. After vaccination, the levels of hepatitis B surface antibody titre (HBs Ab) have been shown to decrease over time. Protective antibodies created by the Hepatitis B virus (HBV) vaccine last for a long time after primary immunization, however there is evidence that the ability to preserve immunological memory declines as time passes following vaccination. The goal of this study was to see how long protective antibody levels lasted after a basic course of hepatitis B vaccination in people at the age of 20. The HBsAb levels of 100 vaccinated subjects (aged 20 years) were evaluated using an enzyme-linked immunosorbent test in a cross-sectional study. Hepatitis B seroprotection rate (anti HBsAb ≥ 10 IU/L) among vaccinated subjects was 62% ranging from (11 to 538.3) with geometric mean titre (81.5±117.28), while 38% of subjects showed non- protective antibodies (anti HBsAb < 10 IU/L) ranging from (0.8 to 9.5) with geometric mean titre (4.29 ± 2.40). The geometric mean titer of HBsAb levels was found to be dropping. The findings revealed a downward trend in HBsAb titers in our region 20 years following hepatitis B virus immunization. More research is needed to determine whether a booster dosage is required in persons who might catch hepatitis B virus infection due to their risky work.