It is well recognized that older adults can contract pertussis, suffer its complications, and unwittingly transmit it to close contacts, which may well include infants too young to have received their primary series of DTaP vaccinations. ADACEL® vaccine is currently licensed in the US for persons 11 - 64 years of age, but no pertussis vaccine is yet approved for administration to older adults. The most widely used Td vaccine in the US, DECAVAC®, has no upper limit on its age indication.

The purpose of this trial is to describe the safety and immunogenicity of ADACEL® vaccine among individuals ≥ 65 years of age.

Inclusion Criteria :

• Ambulatory and not institutionalized.
• At least 65 years of age at the time of vaccination.
• Signed Institutional Review Board (IRB)-approved informed consent form.
• Able to attend all scheduled visits and to comply with all trial procedures.

Exclusion Criteria :

• Any condition which, in the opinion of the investigator, would pose a health risk to the participant or interfere with the evaluation of the vaccine.

• Serious chronic disease (eg, cardiac, renal, neurologic, metabolic, rheumatologic, psychiatric) that is unstable or that, in the opinion of the investigator, might:

  • interfere with the ability to participate fully in the study; or
  • interfere with evaluation of the vaccine.

• Known or suspected impairment of immunologic function, including use of immune suppressive medications (eg, rheumatoid arthritis drugs such as methotrexate; cancer chemotherapy agents such as vincristine).

• Febrile illness within the last 72 hours or an oral temperature ≥ 100.4°F (≥ 38°C) at the time of inclusion.

• Any history of documented tetanus, diphtheria or pertussis disease.

• Known or suspected receipt of a tetanus, diphtheria or acellular pertussis containing vaccine within the preceding 5 years.

• Administration of immune globulin or other blood products within the last three months, or systemic corticosteroid therapy (prednisone or equivalent) for more than 2 consecutive weeks within the past 6 months.

• Systemic antibiotic therapy within the 72 hours prior to enrollment.

• Received any vaccine, other than influenza vaccine, in the 30-day period prior to enrollment or scheduled to receive any vaccine, other than influenza vaccine, in the 35-day period after enrollment. For influenza vaccine only, defer if received in the 14-day period prior to enrollment or scheduled to receive in the 14-day period after enrollment.

• Suspected or known hypersensitivity to any of the vaccine components.

• Participation in another interventional clinical trial in the 4 weeks preceding enrollment or planning to participate in another interventional clinical trial during the planned period of this study.

• Use of alcohol or drugs in a manner that may, in the opinion of the investigator, interfere with the subject's ability to comply with trial visits or procedures.

• Thrombocytopenia or bleeding disorder contraindicating intramuscular vaccination.

• Subject deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized without his/her consent, or requires a legally authorized representative.