The aims of this study are to compare the immunogenicity and safety of the GSK Biologicals' combined DTaP-IPV vaccine with separate administration of DTaP and IPV vaccines, when administered as a fifth dose of acellular pertussis vaccine to children aged 4 to 6 years when co-administered with MMR vaccine in subjects who had previously received four doses of Infanrix, three doses of poliovirus-containing vaccine and MMR vaccination.

Inclusion Criteria:

• Healthy children between and including 4 and 6 years of age.
• Previously received 4 doses of GSK Biologicals' DTaP, 3 doses of IPV vaccine and 1 dose of measles, mumps, and rubella vaccine.

Exclusion Criteria:

• Use of any investigational or non-registered drug or vaccine other than the study vaccines within 30 days preceding the administration of study vaccines, or planned use during the study period.
• Chronic administration or planned administration of immunosuppressants or other immune modifying drugs within six months prior to study vaccination or planned administration during the study period
• Administration of immunoglobulins and/or blood products within 3 months prior to vaccination.

Patient-level data for this study will be made available through www.clinicalstudydatarequest.com following the timelines and process described on this site.