The study objective is to assess the immunogenicity and safety of DTaP-IPV combination vaccine administered as a boosting dose to healthy 4 to 6-year-old children who received three doses of primary immunization against diphtheria, tetanus, pertussis, and polio.

Inclusion Criteria:

1. A subject's parent/legal representative provides a written consent after being informed about the study objective, methods, effect of the study vaccine, and other relevant information
2. Documented record of the three doses of primary immunization against diphtheria, tetanus, pertussis, and polio either by participating in the previous study, BR-DTPP-CT-301 or by following the national immunization schedule under usual clinical setting (the primary immunization should have been initiated after 6 weeks of age and at minimal interval of 4 weeks)
3. Receipt of a boosting dose against diphtheria, tetanus, and pertussis until 2 years of age; therefore, total of four vaccination records against diphtheria, tetanus, and pertussis and three against polio
4. Healthy male or female children, aged 4 to 6 years on the day of the vaccination

Exclusion Criteria:

1. Children aged 7 years or older
2. Previously received DTaP vaccine five times or more, including the doses received in the BR-DTPP-CT-301 study, either by a combination vaccine or a separate vaccine
3. Previously received IPV vaccine four times or more, including the doses received in the BR-DTPP-CT-301 study, either by a combination vaccine or a separate vaccine
4. The fourth dose of DTaP vaccine was postponed and administered after 4 years of age
5. Acute febrile illness with fever ≥ 38.0°C (tympanic) on the day of the vaccination
6. Moderate to severe systemic acute illness with or without fever
7. History of diphtheria, tetanus, pertussis, or polio (poliomyelitis)
8. Dysfunctional immune system or congenital or acquired immunodeficiency
9. Had encephalopathy of unknown etiology within 7 days following a previous dose of DTaP vaccine
10. Received a vaccine other than the protocol-permitted vaccines within 28 days from the study vaccination day or are planned to receive such a vaccine during the study period
11. Received systemic corticosteroid treatment at immunosuppressive dosage within 28 days from the study vaccination day or are planned to receive such a treatment during the study period (exceptionally, administration of prednisolone ≤ 0.5 mg/kg/day for up to 14 continuous days is allowed)
12. Received immunoglobulins or blood products within 90 days before the study vaccination day or are planned to receive such products during the study period
13. Had severe allergic reaction (e.g. anaphylaxis) to ingredients of the investigational product or bears such a possibility
14. Currently enrolled in another clinical trial or planned to participate in another clinical trial
15. Any other reasons that preclude the eligibility of the subject, based on investigator's decision