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
Condition: Acellular Pertussis; Tetanus; Diphtheria
MeSH terms: Diphtheria
Study type: Interventional
Phase: Phase 3

Summary: 
      The purpose of this study is to evaluate the persistence of antibodies against all the
      vaccine antigens 1, 3, 5 and 9 years after an initial vaccination with Tdap, and also to
      assess immunogenicity and safety of another dose of Boostrix, administered in this study.

      This protocol posting deals with objectives and outcome measures of the extension phase. The
      objectives and outcome measures of the primary phase are presented in a separate protocol
      posting (NCT number = NCT00346073).
    

Detailed description: 
      Subjects were previously vaccinated with either Boostrix or a control Tdap vaccine (Sanofi
      Pasteurs' Adacel) in study NCT00346073. Only subjects who were part of the primary study will
      be invited to participate in this study. All subjects will receive a single dose of Boostrix
      at Visit 6 (Day 0) and subjects will be observed till Visit 7 (Day 30) for safety in terms of
      solicited adverse events (during 4 days post vaccination), unsolicited adverse events (during
      31 days post vaccination) and serious adverse event (during the trial period). A blood sample
      will be collected from all subjects before vaccination (Visit 6) and one month after
      vaccination (Visit 7) for antibodies estimation.

      This summary has been updated following Protocol amendment 1 dated 09 November 2010,
      amendment 2 dated 18 February 2014, and amendment 3 dated 10 December 2014. The protocol was
      amended first due to the following reasons:

        1. The maximum window period allowed for the return of subjects for the Year 5 and Year 10
           follow-up visits (Visit 5 and Visit 6) was extended from ± 5 weeks to ± 8 weeks.

        2. The contact details for reporting of SAEs were clarified.

        3. Text pertaining to the reporting of spontaneous abortion was removed from the protocol.

        4. The number of attempts to contact subjects who did not return for scheduled persistence
           visits was clarified.

      The main purpose of protocol amendment 2 is to evaluate the immunogenicity and safety of
      Boostrix as a second dose of Tdap vaccine when administered 8 years after an initial dose of
      Tdap. The Year 10 time point for evaluation of persistence has been cancelled because it is
      no longer feasible to conduct after a second dose of Tdap vaccine has been administered at
      Year 8.

      The purpose of amendment 3 is to add co-primary objective to demonstrate that the immune
      response elicited by a second dose of Tdap vaccine, Boostrix (Boostrix group and Adacel
      group) is non-inferior to the immune response elicited by a first dose of Tdap vaccine
      (Control group), with respect to booster response against diphtheria, tetanus and pertussis
      (PT, FHA and PRN) antigens, one month following vaccination according to CBER's input.
      Accordingly, the study start has been pushed to Year 9 and this is reflected throughout the
      document.
    

Intervention name(s): Taking of blood samples; Boostrix; Adacel
Intervention type(s): Procedure; Biological; Biological
Intervention description(s): No treatment is planned to be given in this study. Blood samples will be collected at the following time points: 1 year, 3 years, 5 years and 9 years after the dose of vaccination.; A single dose of Boostrix was administered in the primary study (NCT00346073). No treatment was given in this study.; A single dose of Adacel was administered in the primary study (NCT00346073). No treatment was given in this study.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Persistence; immunogenicity