1. Healthy Group 1.1 ≥18 years old, 1.2 were negative for hepatitis B surface antigen (HBsAg), antibody to hepatitis B surface antigen (anti-HBs), and antibody to hepatitis B core antigen (anti-HBc), had no history of previous vaccine 1.3 were negative for antibody to hepatitis C virus (anti-HCV) 1.4 received three intramuscular injections of 20 μg of recombinant HBV vaccine (Hepavax-Gene® Berna, Korea) at months 0, 1, and 6 during February 4, 2011 to May 4, 2012, the same time as the study under ClinicalTrials.gov; NCT1289106. were conducted.