The present clinical study will assess the immunogenicity and reactogenicity of Sanofi Pasteur's DTacP-IPV// PRP~T combined vaccine (Pentavac™ or Pentaxim™) as a three-dose primary vaccination at 2, 4, and 6 months of age followed by a booster dose during the second year of life and concomitant hepatitis B vaccine at 2 and 6 months of age in infants in Thailand.