Immunogenicity, Safety & Reactogenicity of GSK Vaccine Tritanrix™-HepB/Hib2.5 Compared to GSK Vaccine Tritanrix™-HepB/Hiberix™

Inclusion Criteria: * Subjects who the investigator believes that their parents/guardians can and will comply with the requirements of the protocol should be enrolled in the study. * A male or female between, and including, 6 and 8 weeks of age at the time of the first vaccination. * Written informed consent obtained from the parent or guardian of the subject. * Free of obvious health problems as established by medical history and clinical examination before entering into the study. * Born after a gestation period of 36 to 42 weeks. * Born to a mother proven seronegative for HBsAg. Exclusion Criteria: * Planned administration/ administration of a vaccine not foreseen by the study protocol within 30 days before each dose of vaccine, with the exception of oral polio vaccine (OPV). * Bacille Calmette-Guérin (BCG) vaccine received after the first 2 weeks of life. * Use of any investigational or non-registered drug or vaccine other than the study vaccine(s) within 30 days preceding the first dose of study vaccine, or planned use during the study period. * Chronic administration of immunosuppressants or other immune-modifying drugs since birth. * Previous vaccination against diphtheria, tetanus, pertussis, hepatitis B and/or Hib. * History of, or intercurrent, diphtheria, tetanus, pertussis, hepatitis B and/or Hib disease. * Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection. * A family history of congenital or hereditary immunodeficiency. * History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. * Major congenital defects or serious chronic illness. * History of any neurologic disorders or seizures. * Acute disease at the time of enrolment. * Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination or history. * Administration of immunoglobulins and/or any blood products since birth or planned administration during the study period. * Other conditions which in the opinion of the investigator may potentially interfere with interpretation of study outcomes.