The aim of the current study was to evaluate viral suppression following combined treatment with an S/pre-S1/pre-S2 vaccine and lamivudine in patients with chronic hepatitis B. We established a randomized, controlled clinical trial to compare the responses of three different treatment groups: those receiving vaccine monotherapy, lamivudine monotherapy, or combination treatment. Viral response was evaluated via hepatitis B virus (HBV) DNA suppression using different levels of classification. Seroconversion was evaluated via HBeAg loss, HBeAg seroconversion, HBsAg loss, and anti-HBs response. We found that the group receiving combination treatment demonstrated a significant increase in viral suppression over that for the lamivudine or vaccine monotherapy group, although the HBeAg seroconversion rate was not different. This enhanced suppression effect in the combination group was reversed after the discontinuation of vaccine treatment, suggesting that booster doses are required for a sustained viral response. Anti-HBs was detected in 55/120 vaccine recipients, but only 3 patients demonstrated HBsAg loss, indicating that the vaccine-induced anti-HBs was unable to completely neutralize HBsAg in the serum. At the study end point, anti-HBs responders showed significantly higher HBeAg seroconversion rates, greater suppression of HBV DNA levels, and a lower median reduction in HBV DNA levels than those of anti-HBs nonresponders. Our results suggest that combined treatment with the vaccine and lamivudine was significantly more effective than lamivudine monotherapy in the short term and was especially successful in producing viral suppression and an enhanced anti-HBs antibody response.