Primary objective:

• To describe in subjects vaccinated with 3 doses of HEXAVAC® or 3 doses of INFANRIX®-HEXA during the first two years of life the percentage of subjects with an anti-HBs antibody titre ≥10 mIU/mL 1 month after a booster dose of either HBVaxPRO® 5 µg or Engerix B® 10 µg .

Secondary objectives:

• Additional immunogenicity assessments
• Standard safety assessment.

Inclusion Criteria:

• Healthy child of 4 to 7 years of age of either gender,
• Child vaccinated with 2 doses of HEXAVAC® during the first 6 months of life and with a 3rd dose of HEXAVAC® before the end of the second year of life or Child vaccinated with 2 doses of INFANRIX®-HEXA during the first 6 months of life and with a 3rd dose of INFANRIX®-HEXA before the end of the second year of life,
• Informed consent form signed by the parent(s) or by the legal representative.
• Parent(s) or legal representative able to understand and comply with the study procedures.

Exclusion Criteria:

• Any recent (<=3 days) history of febrile illness prior to vaccination,
• Receipt of more than 3 doses of any Hepatitis B containing vaccine, either alone or in any combination,
• History of clinical or serological-confirmed diagnosis of infection due to hepatitis B,
• History or current close contact with known carriers of hepatitis B virus,
• Prior known sensitivity/allergy to any component of the study vaccines,
• Any known blood dyscrasias, leukemia, lymphomas of any type, or other malignant neoplasms affecting the haematopoietic and lymphatic systems,
• Any severe thrombocytopenia or any other coagulation disorder that would contraindicate intramuscular injection,
• Any immune impairment or humoral/cellular deficiency or depressed immunity,
• Any recent (<=30 days) long-term (>=14 days) administration of systemic corticosteroids given daily or on alternate days at >=20 mg/day prednisone equivalent or scheduled administration through Visit 2,
• Any receipt (<=3 months) of immunoglobulins or blood-derived products, or scheduled administration through Visit 2,
• Any recent (<=14 days) receipt of an inactivated vaccine or scheduled administration through Visit 2,
• Any recent (<=28 days) receipt of a live vaccine or scheduled administration through Visit 2