Long-term efficacy of the hepatitis B vaccine in a high-risk group.

Chronic infection with hepatitis B virus (HBV) is a global health problem. In an attempt to control infection, worldwide HBV vaccination programs have been established. Saudi Arabia, an endemic area for HBV infection, established an HBV immunization program in 1989. This cross-sectional study evaluates the long-term protection of HBV vaccination 14-24 years after primary immunization in a high-risk group (clinical year medical students) at King Abdulaziz University Hospital in Jeddah, Saudi Arabia. All participants had complete HBV immunization at birth or in early childhood. Hepatitis B surface antibody (anti-HBs) levels were obtained. An anti-HBs titer of <10 mIU/ml indicated no protection, while a titer of >10 mIU/ml was considered to represent protective immune status. A total of 238 students were included; they were predominantly females (n = 182, 76.5%). Mean age was 22.2 ± 1.1 years. Duration since primary vaccination was 19.8 ± 2.3 years. Female students were more likely to maintain long-term protection compared to males (62.1% and 58.8%, respectively). Anti-HBs levels were significantly low in many students after primary immunization. Testing medical students for anti-HBs levels may be warranted as they represent a high-risk population. The higher rate of vaccine failure in males than females requires further investigation as it may explain the higher prevalence of HBV in the male population.