AIM: Patients with chronic hepatitis C have been recommended to receive vaccinations against hepatitis B. Our study aimed at evaluating the hepatitis B immunogenicity and efficacy against hepatitis B virus infection 4 years after primary immunization series in a group of patients with chronic hepatitis C. METHODS: We recruited 36 out of 48 hepatitis C virus (HCV) infected individuals who were vaccinated against hepatitis B virus (20 μg of recombinant HBsAg at 0-1-6 mo schedule) in 1998. Here we measured anti-HBs titers and anti-HBc 4 years after delivery of the third dose of primary immunization series. RESULTS: After 4 years a total of 13/36 (36%) HCV infected patients had seroprotective titers of anti-HBs compared with 9/10 (90%) in the control group, (P<0.05). Similarly the mean concentration of anti-HBs found in hepatitis C patients was significantly lower than that found in healthy subjects (18.3 and 156.0 mIU/mL respectively (P<0.05). None of the HCV infected patients or controls became infected with HBV during the study period as confirmed by anti-HBc negativity. CONCLUSION: We demonstrated that 4 years after HBV immunizations’ more than 60% of vaccinated HCV patients did not maintain seroprotective levels of anti-HBs, which might put them at risk of clinically significant breakthrough infections. Further follow-up studies are required to clarify whether memory B and T lymphocytes can provide protection in chronic hepatitis C patients in the absence or inadequate titers of anti-HBs. AIM: Patients with chronic hepatitis C have been recommended to receive vaccinations against hepatitis B. Our study aimed at evaluating the hepatitis B immunogenicity and efficacy against hepatitis B virus infection 4 years after primary immunization series in a group of patients with chronic hepatitis C. METHODS : We recruited 36 out of 48 hepatitis C virus (HCV) infected individuals who were vaccinated against hepatitis B virus (20 μg of recombinant HBsAg at 0-1-6 mo schedule) in 1998. Here we measured anti-HBs titers and anti- HBc 4 years after delivery of the third dose of primary immunization series. RESULTS: After 4 years a total of 13/36 (36%) HCV infected patients had seroprotective titers of anti-HBs compared with 9/10 (90%) in the The mean concentration of anti-HBs found in hepatitis C patients was significantly lower than that found in healthy subjects (18.3 and 156.0 mIU / mL respectively. (P <0.05). None of the HCV infected patients or control s became infected with HBV during the study period as confirmed by anti-HBc negativity. CONCLUSION: We demonstrated that 4 years after HBV immunizations’ more than 60% of vaccinated HCV patients did not maintain seroprotective levels of anti-HBs, which might put them at risk of clinically significant breakthrough infections. Further follow-up studies are required to clarify whether memory B and T lymphocytes can provide protection in chronic hepatitis C patients in the absence or inadequate titers of anti-HBs.