In July 2015-November 2016, a phase II/III randomized, observer-blind,controlled study of two acellular Pertussis vaccines (aP standalone and TdaP combined vaccines) manufactured by BioNet-Asia Co., Ltd. (Bionet) and chemically-detoxified Adacel Tdap vaccine was conducted in Bangkok, Thailand in healthy participants aged 12-17 years (Protocol No. TDA202; http://clinicaltrials.in.th;Study ID:TCTR20150703002). A total of 450 participants were enrolled into the study at 2 study sites (Site No.1:Faculty of Medicine Siriraj Hospital; Site No.2:Vaccine Trial Centre (VTC), Faculty of Tropical Medicine, Mahidol University) with equal number of 225 participants enrolled at each study site. During the study, the participants had been randomized in a 1:1:1 ratio to received intramuscularly a booster dose (0.5 mL) of the study vaccines.

This is further follow-up from TDA202 clinical trial, which was completed on 29 November 2016. Target population for this study is the group of participants who had received one dose of one of the three study vaccines in the TDA202 trial at site VTC and who had completed the study follow-up at 1-year after vaccination (223 subjects).

In this current study, the long-term persistence of pertussis antibodies induced by a booster dose of recombinant acellular Pertussis based vaccines (Pertagen and Boostagen) manufactured by Bionet will be evaluated and compared to the conventional chemically-inactivated Tdap vaccine (Adacel) at 5 years after previously immunized in the TDA202 study.

The study population will included all participants who participated in the TDA202 study at the Vaccine Trial Centre (VTC), Faculty of Tropical Medicine, Mahidol University, Bangkok.

Participants from all 3 vaccine groups (i.e., participants who had received a single dose of one of the 3 study vaccines (Boostagen®, Pertagen®, or Adacel®) and completed 1-year follow-up visit at Day 336±28 days during the TDA202 study will be called in for informed consent process at Visit 1 at approximately 5 years after vaccination (±56 days) based on Vaccination Date in the TDA202 study. Participants aged ≥18 years who have signed the written Informed Consent Form or participants aged less than 18 years who have co-signed the Informed Consent Form with their parent/legal will be screened for general health status (a survey for medical history, immunization history, history of receiving blood, blood component, immunoglobulin, immunosuppressive drugs or systemic corticosteroid and physical examination) and those who fulfill the pre-defined inclusion criteria and do not meet an exclusion criteria will be enrolled into the study.

Once enrolled, a blood sample (approx. 5 mL) will be taken from all participants. After blood collection, this will be considered as study end for all participants. Participants will be offered a licensed influenza vaccine at the end of Visit 1.

Blood samples collected from all participants who have come back for the 5-year follow-up visit (Visit 1) will be processed for serum preparation. Serum samples will be stored at the laboratory at the study site and will be further shipped to BioNet Human Serology Laboratory where immunogenicity testing (ELISA antibodies against Pertussis Toxin (PT), Filamentous hemagglutinin (FHA), Diphtheria Toxin (DT), and Tetanus Toxin (TT) and PT-neutralizing antibody by Chinese Hamster Ovary (CHO) cells assay) will be performed. ELISA testing to detect antibodies against tetanus, diphtheria, and pertussis antigens (PT and FHA) will be performed for all enrolled participants while CHO cells assay to detect PT-neutralizing antibody will be performed only in the same subset of participants who had been selected for PT-neutralizing antibody study in the initial TDA202 study.

The knowledge from this long-term 5-year antibody persistence study will provide supportive data to identify the best alternative acellular pertussis vaccines to conventional chemically-inactivated vaccines for controlling the resurgence of pertussis disease.

Data management and statistical analysis will be performed by Center of Excellence for Biomedical and Public Health Informatics (BIOPHICS), Bangkok, Thailand.

Inclusion Criteria:

A participant will be eligible for inclusion if ALL of the followings apply at the time of screening:

1. Having participated in the initial TDA202 study, received a single dose of one of the 3 study vaccines, and completed 1-year follow-up visit;
2. Written informed consent is obtained for participants aged ≥18 years, or written informed consent are obtained from participants aged <18 years with their parents/legal guardians, co-signed prior to study entry;
3. Healthy, as established by pertinent medical history and physical examination;
4. Capable of complying with study procedures and willing to provide with a blood sample

Exclusion Criteria:

1. Having received pertussis vaccine since TDA202 study

The target population for this study is the group of participants who had received one dose of acellular pertussis based vaccine in TDA202 trial at Vaccine Trial Centre (VTC), Faculty of Tropical Medicine, Mahidol University and who had completed the study follow-up at 1 year after vaccination.