This study will assess the immunogenicity of GlaxoSmithKline (GSK) Biologicals' (formerly SmithKline Beecham Biologicals') DTPa-HBV-IPV/Hib (Infanrix hexa™) vaccine compared to the separate administration of DTPa-HBV-IPV (Infanrix™ penta) and Hib (Hiberix™) vaccines administered at 3 and 5 months of age.

Inclusion Criteria:

• A male or female between 12 and 16 weeks of age at the time of the first vaccination.
• Free of obvious health problems as established by medical history and clinical examination before entering into the study.
• Written informed consent obtained from the parents or guardians of the subject after they have been advised of the risks and benefits of the study in a language which they clearly understood, and before performance of any study procedure.

Exclusion Criteria:

• Use of any investigational or non-registered drug or vaccine other than the study vaccine(s) during the study period or within 30 days preceding the first dose of study vaccine.
• Administration of chronic immunosuppressants or immune-modifying drugs during the study period.
• Administration of a vaccine not foreseen by the study protocol during the period starting from one month before each dose and ending one month after each dose.
• Previous vaccination against diphtheria, tetanus, pertussis, hepatitis B, polio and/or Hib diseases.
• History of/or intercurrent diphtheria, tetanus, pertussis, hepatitis B, polio and/or Hib disease.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection.
• History of allergic disease or reaction likely to be exacerbated by any component of the vaccine, including allergic reactions to neomycin and polymyxin B.
• Major congenital defects or serious chronic illness.
• Progressive neurological disorders.
• Administration of immunoglobulins and/or any blood products since birth and during the study period.
• Acute febrile illness at the time of planned vaccination.