Prevention of hepatitis B infection in drug users: Effectiveness of accelerated versus standard HBV vaccination schedule

Background: Despite the availability of a highly efficacious vaccine, Hepatitis B still remains a highly prevalent infection in drug users, due to low acceptance and adherence to standard HBV vaccination. An accelerated schedule has been demonstrated to overcome this obstacle in our earlier study; however, its long-term effectiveness remains unexamined. Methods: We compared long-term effectiveness of accelerated vaccination schedule (0-1-2month) with standard vaccination schedule (0-1-6month) in preventing HBV infections in drug users. HBV infection rate and anti-HBs antibody loss during 2 year follow-up were determined in 707 drug users, who were free of HIV and HBV infections at enrollment and completed 3 doses of vaccination during an HBV vaccination intervention trial. Incidence rates were computed by Kaplan-Meier life tables and failure curves were compared by Wilcoxon tests. Associated risk factors for these outcomes were identified by Cox proportional hazards model. Results: Accelerated schedule had significantly lower cumulative incidence of HBV infection compared to standard schedule (1.15% vs. 2.54%, p<0.05). No chronic infections were observed during the 2 year follow-up. There was no significant difference in anti-HBs antibody loss between the 2 schedule groups. Hepatitis C infection at enrollment and age <40 years were identified as independent risk factors for HBV infection and antibody loss, respectively. Conclusions: Accelerated schedule is more effective than standard schedule in preventing HBV infections in drug users. To overcome the disadvantages of standard schedule such as longer duration for adherence and continued high risk behavior until completion of three vaccine doses, accelerated vaccination schedule should be considered in drug using population.