Persistence Study of GSK Biologicals' Tdap Vaccine 1, 3, 5 and 9 Years Following Administration as an Initial Single Dose in Healthy Young Adults and to Evaluate the Immunogenicity and Safety of Boostrix as a Second Dose of Tdap, When Administered at Year 9

Inclusion Criteria: • Persistence follow-up phase up to Year 9 time point: The following criteria are applicable to subjects who refuse vaccination at Year 8 time point: All subjects who received study vaccination (Boostrix or Adacel) in study NCT00346073 will be considered eligible to participate in this study. Written informed consent must be obtained from the subject prior to each study time point. Vaccination phase at Year 9 applicable for subjects in Boostrix and Adacel groups only: The following criterion is applicable to subjects willing to consent to vaccination at Year 9 time point in the Boostrix and Adacel groups: • All subjects who received study vaccination (Boostrix or Adacel) in study NCT00346073 will be considered eligible to participate in this study. Vaccination phase at Year 9 applicable for subjects in the Control group only: The following criterion is applicable to subjects willing to consent to vaccination at Year 9 time point in the Control group only: • Subjects within the age range of 28-73 years will be considered eligible to participate in this study in the Control group. Vaccination phase at Year 9 applicable for ALL subjects (Control, Boostrix and Adacel groups): The following criteria are applicable to subjects willing to consent to vaccination at Year 9 time point in the Boostrix, Adacel and Control groups: All subjects must satisfy the following criteria at study entry at Year 9 time point: Subjects who, in the opinion of the inve…