A Study on the Immune Response and Safety of a Combined Vaccine Against Diphtheria, Tetanus and Acellular Pertussis (dTpa) in Healthy Japanese Adolescents Aged 11 Years to <13 Years

A Phase 3, Non-randomized, Single-arm, Open-label Study to Assess the Immunogenicity, Safety and Reactogenicity of Combined Reduced-antigen-content Diphtheria, Tetanus and Acellular Pertussis (dTpa) Vaccine, Administered as a Booster Dose in Healthy Japanese Adolescents Aged 11 Years to <13 Years

The purpose of the study is to assess the immune response, reactogenicity and safety of a booster dose of dTpa vaccine 1 month after vaccination in healthy Japanese participants aged 11 to <13 years.

Study Overview

• Status: Not yet recruiting
• Conditions: Diphtheria-Tetanus-acellular Pertussis Vaccines
• Intervention / Treatment: Biological: dTpa vaccine

• Study Type: Interventional
• Enrollment (Estimated): 85
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: US GSK Clinical Trials Call Center; Phone Number: 877-379-3718; Email: GSKClinicalSupportHD@gsk.com
• Study Contact Backup: Name: EU GSK Clinical Trials Call Center; Phone Number: +44 (0) 20 89904466; Email: GSKClinicalSupportHD@gsk.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Participants and/or participants' parent(s)/ Legally acceptable representative(s) [LAR(s)], who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
• Physical or digital informed assent obtained from the participant prior to performance of any study-specific procedure.
• Physical or digital informed consent obtained from the parent(s)/LAR(s) of the participant prior to performance of any study-specific procedure.
• Healthy participants as established by medical history and clinical examination at screening.
• Male/female participant between and including 11 and <13 years of age at the time of the study intervention administration (Visit 1/Day 1).
• Previously completed all routine childhood vaccinations to the best knowledge of the participant's parent(s)/LAR(s). Participants with documented previous diphtheria, tetanus and pertussis vaccination (primary series and first booster) as per routine vaccination in Japan prior to study enrolment.
• Participants did not receive an additional diphtheria, tetanus with or without pertussis vaccination within 5 years prior to enrolment in the study.
• Japanese ethnic origin.
• Participants of non-childbearing potential may be enrolled in the clinical study.
• Participant of childbearing potential may be enrolled in the study if the participant:
• has practiced adequate contraception for at least 30 days prior to study intervention administration, and
• has a negative pregnancy test within 24 hours prior to the study intervention administration, and
• has agreed to continue adequate contraception during the entire treatment period and for 8 weeks after completion of the study intervention administration series.

Exclusion Criteria:

Medical conditions

• History of physician-diagnosed or laboratory-confirmed diphtheria, tetanus or pertussis diseases within the past 5 years.
• History of encephalopathy after administration of a previous dose of pertussis vaccine that could not be attributed to another identifiable cause, progressive neurologic disorder, uncontrolled epilepsy or progressive encephalopathy: pertussis vaccine should not be administered to individuals with these conditions until a treatment regimen has been established and the condition has stabilized.
• History of transient thrombocytopenia or neurological complications following an earlier immunization against diphtheria and/or tetanus.
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the study intervention(s) or having shown signs of hypersensitivity after previous administration of diphtheria, tetanus or pertussis vaccines.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination
• Acute or unstable chronic conditions clinically significant pulmonary, cardiovascular, hepatic, or renal functional abnormality, as determined by physical examination and/or laboratory screening tests.
• Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the clinical study.
• Condition that in the judgment of the investigator would make intramuscular injection unsafe.

Prior/Concomitant therapy

• Use of any investigational or non-registered product other than the study intervention(s) during the period beginning 30 days before the dose of study intervention(s), or their planned use during the study period.
• Administration of immunoglobulins or other blood products or plasma derivatives during the period starting 90 days before the study intervention or planned administration during the study period.

• Chronic administration of immune-modifying drugs and/or planned use of long-acting immune-modifying treatments at any time up to the end of the study.

  • Up to 6 months prior to the study intervention administration:

For corticosteroids, this will mean prednisone equivalent ³0.5 mg/kg/day with maximum of 20 mg/day. Inhaled, intra-articular/intra-bursal and topical steroids are allowed.

• Up to 6 months prior to study intervention administration: long-acting immune-modifying drugs including among others immunotherapy, monoclonal antibodies, antitumoral medication.

  • Planned administration/administration of a vaccine not foreseen by the study protocol in the period starting 30 days before the dose and ending 30 days after the dose of study intervention(s) administration*, with the exception of inactivated influenza vaccine and SARS-CoV-2 vaccine which can be given at any time during the study conduct.

    *If emergency mass vaccination for an unforeseen public health threat (e.g., a pandemic) is recommended and/or organized by public health authorities outside the routine immunization program, the time period described above can be reduced, provided it is used according to the local governmental recommendations and Sponsor is notified.

  • Planned administration of any prophylactic medication in the absence of any symptom and in anticipation of a reaction to the study intervention administration.

Prior/Concurrent clinical study participation

• Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non-investigational intervention vaccine/drug/invasive medical device.

Other exclusion criteria

• Pregnant or lactating participant.
• History of /current chronic alcohol consumption and/or drug abuse, based on investigator's judgment.
• Any study personnel or their immediate dependents, family, or household members.
• Child in care.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Non-Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: dTpa Group; Participants aged 11 to less than (<) 13 years receive the dTpa vaccine at Day 1.	Biological: dTpa vaccine; Combined reduced antigen content diphtheria, tetanus and acellular pertussis (dTpa) vaccine administered at Day 1.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of seropositive participants for anti-pertussis toxin (anti-PT), anti-filamentous hemagglutinin (FHA) and anti-pertactin (PRN) antibodies	Seropositivity is defined as antibody concentrations (anti-PT, anti-FHA and anti-PRN) are greater than or equal to the assessed assay cut-offs. The considered cut-off values are: anti-PT: 2.693 International Units per milliliter (IU/mL), anti-FHA: 2.046 IU/mL, anti-PRN: 2.187 IU/mL, as measured by Enzyme-Linked Immunosorbent assay (ELISA).	1 month after vaccination
Number of seroprotected participants for anti-diphteria and anti-tetanus antibodies	Seroprotection is defined as anti-diphtheria and anti- tetanus antibody concentrations being >=0.1 IU/mL as measured by ELISA.	1 month after vaccination

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of participants with booster-response to pertussis (PT, FHA and PRN) antigens	Booster response to PT, FHA and PRN antigens is defined as: for participants with pre-vaccination antibody concentration below the assay cut-off, post-vaccination antibody concentration >=4 times the assay cut-off; for participants with pre-vaccination antibody concentration between the assay cut-off and below 4 times the assay cut-off, post-vaccination antibody concentration >= 4 times the pre-vaccination antibody concentration; for participants with pre-vaccination antibody concentration >=4 times the assay cut-off, post-vaccination antibody concentration >=2 times the pre-vaccination antibody concentration.	1 month after vaccination
Antibody concentration against pertussis (PT, FHA, PRN) antigens		At baseline (Day 1) and 1 month after vaccination
Antibody concentration for anti-diphtheria and anti-tetanus antibodies		At baseline (Day 1) and 1 month after vaccination
Number of participants with solicited local adverse events (AEs)	Solicited local AEs are pain, redness (erythema) and swelling at administration site.	From Day 1 (day of vaccination) to Day 7 post-vaccination
Number of participants with solicited systemic AEs	Solicited systemic AEs are fever, headache, myalgia (muscle pain), arthralgia (joint pain), fatigue (tiredness) and gastrointestinal symptoms.	From Day 1 (day of vaccination) to Day 7 post-vaccination
Number of participants with unsolicited AEs	An unsolicited AE is an AE that was either not included in the list of solicited AEs or could be included in the list of solicited AEs but with an onset outside the specified period of follow-up for solicited AEs. Unsolicited AEs include both serious and non-serious AEs.	From Day 1 (day of vaccination) to Day 30 post-vaccination
Number of participants with serious AEs (SAEs)	An SAE is defined as any untoward medical occurrence that, at any dose, results in death, is life threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect in the offspring of a study participant, abnormal pregnancy outcomes, is a suspected transmission of any infectious agent via an authorized medicinal product, or other situations as per investigator's judgment.	From Day 1 (day of vaccination) to Day 30 post-vaccination
Number of participants with AEs leading to study withdrawal		From Day 1 (day of vaccination) to Day 30 post-vaccination

Collaborators and Investigators

• Sponsor: GlaxoSmithKline

Study record dates

Study Major Dates

• Study Start (Estimated): June 29, 2026
• Primary Completion (Estimated): October 14, 2026
• Study Completion (Estimated): October 14, 2026

Study Registration Dates

• First Submitted: May 13, 2026
• First Submitted That Met QC Criteria: May 13, 2026
• First Posted (Actual): May 19, 2026

Study Record Updates

• Last Update Posted (Actual): May 19, 2026
• Last Update Submitted That Met QC Criteria: May 13, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Adolescent; Safety; Reactogenicity; Immune response; Diphtheria tetanus and acellular pertussis (dTpa) vaccine
• Other Study ID Numbers: 308734

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/gsk-patient-level-data-sharing-july2025.pdf
• IPD Sharing Time Frame: Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or asset(s) with development terminated across all indications.
• IPD Sharing Access Criteria: Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months, but an extension may be granted, when justified, for up to 6 months.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No