Background: Insufficient immune response to hepatitis B virus (HBV) vaccine in diabetics is frequently encountered and anti-HBs levels may persist for a shorter time than among immune competent persons. The present study was conducted to determine long–term persistence of anti-HBs among Egyptian diabetic school students and to assess the need and response to a subsequent challenge with vaccine booster doses. Methods: The study included two phases, a comparative (screening) phase followed by a quasi-experimental (boosting) phase. A baseline serologic screening for anti-HBs titre was carried out among 260 school students aged 10-17 years (130 diabetics and 130 healthy non-diabetics, matched for age and sex) who received the full threedose regimen of HBV vaccine under the Expanded Program of Immunization (EPI) in Egypt. Ninety participants (45 diabetic and 45 healthy ones) with anti-HBs<10 m IU/mL consented to be enrolled in the second phase to receive additional booster doses of the vaccine. Results: The median value of anti-HBs titre was significantly lower among diabetics (3.0 m IU/mL) as compared to non-diabetics (6.8 m IU/mL). Age was the only significant risk factor associated with poor response. Adequate protection (anti-HBs>100 mIU/ml) was achieved after receiving two doses of the vaccine for healthy students and three doses for diabetics. BMI and history of hospitalization due to diabetes were the only significant factors affecting the response to boosting among diabetic students. In conclusion, type 1 DM adolescents express hyporesponsivness to HBV vaccination and more rapid decline of protective anti-HBs compared to healthy ones. A booster dose of HBV vaccine would be recommended at age 12 years for diabetic students.