Patients: Patients who have been receiving entecavir or tenofovir therapy for at least 30 months will be invited to this study. The case group will receive 5 Engerix-B injections during the last 6 months of entecavir or tenofovir therapy. Arm A-entecavir pretreated group: 75 cases will be enrolled to receive Engerix-B injection and compared with histological non-vaccine treated controls; Arm B-tenofovir pretreated group: 50 patients will be randomized into case (vaccine) and control group according to age, gender, pretreatment HBV DNA level.