AIM: (1) To gain information on immune responses to an accelerated schedule of 0,1, and 2 mo in paramedical staff and BDS students who are at an increased risk of getting hepatitis B infection and come under high risk groups. (2) To assess the efficacy and safety of Enivac-HB in different age groups, using genetically modified yeast strain Pichia pastoris, a new recombinant hepatitis B vaccine developed and manufactured in India. METHODS: A prospective, comparative, and single blinded trial of rapid (0, 1, and 2 mo) hepatitis B immunization schedulewas reported. A total of three hundred and seven (212 females and 95 males) healthy volunteers divided into three age groups (18-29, 30-39, and 40-49) were enrolled after screening for markers of hepatitis B. All the volunteers received 20 mg of the vaccine intramuscularly at 0, 1, and 2 mo. RESULTS: Geometric mean titers were calculated pre and post vaccination. Before immunization the GMT was 0.0124 mIU/mL. One month after the administration of the third dose of recombinant vaccine 296/307 (96.5%) subjects achieved seroprotective levels of anti-HBs. The geometric mean anti-HBs titers achieved after one month of the third dose was 2 560.0 mIU/mL The geometric mean anti-HBs titer of males was 2 029.0 mIU/mL, while that of the females was 2 759.0 mIU/mL. In the age group of 18-29 years, anti-HBs titer was 3 025.0 mIU/ mL, while that in the age group of 30-39 years was 2 096.0 mIU/mL. In third age group of 40-49 years, anti-HBs titer was 1 592.0 mIU/mL. Hyper-responses (anti- HBs≥100 mIU/mL) were shown in 88.0% (271/307) of subjects. Eleven (3.5%) subjects responded poorly to the vaccine in the age group of 40-49 years. There was only mild pain at the site of injection otherwise there were no other adverse drug reactions (ADRs). CONCLUSION: This vaccine (Enivac-HB) is safe and efficacious, providing significant protection after the third dose and rapid hepatitis B immunization schedule of 0, 1, and 2 mo can be recommended whenever rapid protection is the goal. AIM: (1) To gain information on immune responses to an accelerated schedule of 0,1, and 2 mo in paramedical staff and BDS students who are at an increased risk of getting hepatitis B infection and come under high risk groups. (2) To assess the efficacy and safety of Enivac-HB in different age groups, using genetically modified yeast strain Pichia pastoris, a new recombinant hepatitis B vaccine developed and manufactured in India. METHODS: A prospective, comparative, and single blinded trial of rapid (0 , 1, and 2 mo) hepatitis B immunization schedulewas reported. A total of three hundred and seven (212 females and 95 males) healthy volunteers divided into three age groups (18-29, 30-39, and 40-49) were enrolled after screening for markers of hepatitis B. All the volunteers received 20 mg of the vaccine intramuscularly at 0, 1, and 2 mo. RESULTS: Geometric mean titers were calculated pre and post vaccination. Before immunization the GMT was 0.0124 mIU / mL. One month after the administrati on the third dose of recombinant vaccine 296/307 (96.5%) subjects achieved seroprotective levels of anti-HBs. The geometric mean anti-HBs titers achieved after one month of the third dose was 2 560.0 mIU / mL The geometric mean anti- HBs titer of males was 2 029.0 mIU / mL, while that of the females was 2 759.0 mIU / mL. In the age group of 18-29 years, anti-HBs titer was 3 025.0 mIU / mL, while that in the age group of 30-39 years was 2 096.0 mIU / mL. Hyper-responses (anti-HBs ≧ 100 mIU / mL) were shown in 88.0 (271/307) of subjects. Eleven (3.5%) subjects responded poorly to the vaccine in the age group of 40-49 years. There was only mild pain at the site of injection otherwise there were no other adverse drug reactions (ADRs CONCLUSION: This vaccine (Enivac-HB) is safe and efficacious, providing significant protection after the third dose and rapid hepatitis B immunization schedule of 0, 1, and 2 mo can be recommended whenever rapid protection is the goal.