The aim of the study is to assess the safety and immunogenicity of GlaxoSmithKline Biologicals' (formerly known as SmithKline Beecham Biologicals) combined diphtheria-tetanus-acellular pertussis vaccine in healthy adults, from the age of 18 onwards, in Australia.

Inclusion Criteria:

• At least 18 years of age at the time of the vaccination
• Written informed consent has been obtained

Exclusion Criteria:

• Evidence of confirmed pertussis disease within the previous 5 years

• History of diphtheria or tetanus vaccination within the past 5 years Females must not be pregnant or lactating They must either surgically sterilized or one year post-menopausal or if they are of childbearing potential, they must be abstinent or have used adequate contraceptive precautions (or one month prior to the booster vaccination, and must agree to continue such precautions for 2 months after completion of the vaccination.

• History of diphtheria or tetanus disease

• History of allergic disease likely to be stimulated by the vaccination

• Major congenital defects or serious chronic illness

• History of progressive neurological disease

• Immunosuppressive therapy

• Any suspected or confirmed immune disorder

• Immunoglobulin therapy or administration of any blood products within the previous three months or during the study period

• Acute febrile illness (>37.5°C, axillary or oral temperature) at the time of planned vaccination

• Administration of an investigational or non registered drug or vaccine within 30 days prior to the start of the present trial

• Simultaneous administration of a vaccine not foreseen by the study protocol, within 30 days prior to the start of the present trial

• Any severe or serious adverse experience having occurred after previous administration of DTP vaccine i.e:

  • an immediate anaphylactic or unacceptable reaction to the investigator's opinion, to a previous dose of diphtheria tetanus pertussis whole-cell vaccine, i.e. :
  • encephalopathy
  • fever > 40.5°C (105°F), rectal temperature, occurring after vaccination with diphtheria tetanus pertussis whole-cell vaccine and not due to another identifiable cause.
  • collapse or shock-like state
  • persistent, inconsolable crying lasting > 3 hours
  • seizures with or without fever
  • systemic allergic or neurologic reactions following a previous dose of tetanus and diphtheria toxoids vaccine

• Exclusion from long term follow-up of antibody persistence : Evidence of confirmed pertussis, diphtheria or tetanus disease or vaccination against these diseases since previous study visit