Currently, there is no 5-component acellular pertussis vaccine licensed for the 5th dose in US children aged 4 to 6 years.This study is aimed at providing evidence of sero-protection, booster response and safety of this formulation as a 5th dose.

Primary Objective:

- To compare the immune responses of Tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) Vaccine to Diphtheria, tetanus and acellular pertussis (DTaP) vaccine (all antigens) when each is administered as a 5th dose and given concurrently, to children aged 4 to 6 years.

Secondary/Observational Objectives:

• To compare the immune responses for pertussis antigens of Tdap Vaccine to DTaP vaccine (for pertussis antigens) when each is administered as a 5th dose and given concurrently, to children aged 4 to 6 years.
• To present the long-term immunogenicity at 1-, 3-, and 5-years post-vaccination after each long-term follow-up.
• To describe the safety profile following vaccine administration.

Inclusion Criteria :

• Healthy, as determined by medical history and physical examination.
• Aged 4 to 6 (< 7) years at the time of study vaccination on Day 0.
• Signed and dated informed consent form that has been approved by the Institutional Review Board (IRB) by the parent or legally authorized representative.
• Signed and dated informed assent form from the subject if required by the IRB.
• Able to attend scheduled visits at Visit 1 and Visit 2 and able to comply with all trial procedures. Subjects will be invited to participate in the long-term immunogenicity follow-up study but a commitment to participate in the long-term is not required as an inclusion criterion.
• Documented vaccination history of 4 previous doses of DAPTACEL according to the recommended national immunization schedule for Diphtheria, tetanus and acellular pertussis (DTaP).

Exclusion Criteria :

• Participation in another clinical trial in the 4 weeks preceding the trial vaccination.
• Planned participation in another clinical trial during the original trial period.
• Congenital or acquired immunodeficiency, immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months, or long-term systemic corticosteroids therapy.
• Systemic hypersensitivity to any of the vaccine components or history of life-threatening reaction to the trial vaccine or a vaccine containing the same substances.
• Chronic illness at a stage that could interfere with trial conduct or completion.
• Blood or blood-derived products received in the past 3 months.
• Receipt of any other vaccine within 30 days prior to study vaccination, or planning to receive another vaccine within 30 days before the Visit 2 blood draw (with the exception of the annual influenza vaccine).
• History of diphtheria, tetanus or pertussis infection (confirmed either serologically or microbiologically).
• Thrombocytopenia or bleeding disorder contraindicating intra muscular vaccination.