A Phase 4 interventional study of Maternal TdaP2gen vaccine and Infant Acellular Pertussis-containing Vaccine in Pertussis, Diphtheria and Tetanus, sponsored by Chiang Mai University. Not yet recruiting at 1 site in Thailand. Open to participants aged 0 Days to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-06-02.
Sponsored by Chiang Mai University · Phase 4, Interventional, and Prevention
Pertussis remains a major global public health problem. In Thailand, pertussis vaccination is recommended during pregnancy at 20-32 weeks' gestation, together with routine childhood diphtheria-tetanus-pertussis vaccination administered as a primary series at 2, 4, and 6 months and booster doses at 18 months and 4-6 years of age.
TdaP2gen, a newly developed combined tetanus, diphtheria, and recombinant genetically detoxified acellular pertussis vaccine containing 2 µg pertussis antigen, has shown favorable safety and non-inferior immunogenicity compared with existing pertussis vaccines. However, data on its use in pregnant women, transplacental antibody transfer, and potential immune interference in infants remain limited.
This study aims to evaluate the safety and immunogenicity of TdaP2gen in pregnant women, assess antibody transfer to newborns, and investigate immune responses to tetanus, diphtheria, and pertussis following primary and booster pertussis-containing vaccinations in infants and toddlers, including comparisons between whole-cell and acellular pertussis-containing vaccine schedules.
Pertussis remains a major global public health problem. In Thailand, pertussis vaccination is recommended for all pregnant women at 20-32 weeks' gestation to protect newborns and young infants against pertussis during early life. In addition, combined diphtheria-tetanus-pertussis vaccination is routinely administered as a primary series at 2, 4, and 6 months of age, followed by booster doses at 18 months and 4-6 years of age.
TdaP2gen is a combined tetanus, diphtheria, and recombinant genetically detoxified acellular pertussis vaccine, containing 2 µg pertussis antigen, which has been recently developed. Previous clinical studies have demonstrated that TdaP2gen is safe and elicits non-inferior immune responses against pertussis compared with the 5 µg recombinant acellular pertussis vaccine (TdaP5gen) and the chemically inactivated Tdap vaccine. However, as TdaP2gen is a newly licensed vaccine in Thailand, data on its safety, immunogenicity in pregnant women, placental antibody transfer to infants, and potential immune interference with infant responses to routine pertussis-containing vaccines remain limited.
Therefore, this study aims to evaluate the safety and immunogenicity of TdaP2gen in pregnant women, assess transplacental antibody transfer to newborns, and investigate its impact on immune responses to diphtheria, tetanus, and pertussis following primary series and booster vaccination up to 15-18 months of age in infants and young children.
This study is divided into 3 phases as follows:
Phase 1 - Maternal and fetal phase: This phase will evaluate the immunogenicity and safety of TdaP2gen vaccination in pregnant women, including immune responses against tetanus, diphtheria, and pertussis, as well as the transplacental transfer of antibodies to newborns.
Phase 2 - Infant phase: This phase will assess immune responses to tetanus, diphtheria, and pertussis in infants following completion of the primary pertussis-containing vaccine series at 2, 4, and 6 months of age, comparing infants who receive whole-cell pertussis-containing vaccines (wP-containing vaccines) with those who receive acellular pertussis-containing vaccines (aP-containing vaccines).
Phase 3 - Toddler phase: This phase will evaluate immune responses to tetanus, diphtheria, and pertussis in toddlers after receiving a pertussis-containing booster vaccination at 15-18 months of age, comparing children who receive whole-cell pertussis-containing vaccines (wP-containing vaccines) with those who receive acellular pertussis-containing vaccines (aP-containing vaccines).
290 studies on the registry are indexed under Whooping Cough; 23 are open to participants now.
This study's planned enrollment of 320 is below the median of 400 across 228 interventional studies indexed under Whooping Cough.
Browse Whooping Cough studies →Chiang Mai University is the lead sponsor of 119 studies on the registry; 12 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Phase 1: Pregnant women
Inclusion Criteria:
Exclusion Criteria:
Phase 2: Infants
Inclusion Criteria:
- All infants born to pregnant women enrolled in Phase 1 who received TdaP2gen vaccination during pregnancy will be eligible for enrollment to Phase 2 study
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Live vaccines
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Maternal TdaP2gen Group
Biological: Maternal TdaP2gen vaccine
Infant Acellular Pertussis-containing Vaccine Group
Biological: Infant Acellular Pertussis-containing Vaccine
Infant Whole-cell Pertussis-containing Vaccine Group
Biological: Infant Whole-cell Pertussis-containing Vaccine
A combined tetanus toxoid, reduced diphtheria toxoid, reduced-dose (2 µg) genetically-detoxified recombinant acellular pertussis vaccine (TdaP2gen)
An infant acellular pertussis (aP)-containing vaccine
An infant whole-cell pertussis (wP)-containing vaccine
Phase 1: Maternal anti-pertussis toxin (PT), anti-filamentous hemagglutinin (FHA), anti-diphtheria toxoid, and anti-tetanus toxoid immunoglobulin G (IgG) geometric mean concentrations and seroresponse rates following TdaP2gen vaccination during pregnancy
Assessment of maternal anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates before TdaP2gen vaccination, after vaccination, and at delivery
Time frame: Pre-vaccination baseline, 4 weeks after vaccination (+/- 14 days), and at delivery
Phase 1: Cord blood anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates at birth
Assessment of anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates in cord blood collected at delivery among infants born to TdaP2gen vaccinated mothers
Time frame: At delivery
Phase 1: Incidence of solicited local and systemic adverse events, serious adverse events, and adverse pregnancy outcomes of TdaP2gen vaccination during pregnancy
Assessment of solicited local and systemic adverse events as well as serious adverse events and adverse pregnancy outcomes among pregnant women receiving TdaP2gen vaccination during pregnancy.
Time frame: From vaccination until delivery, assessed up to approximately 22 weeks post-vaccination.
Phase 2: Infant anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates following primary diphtheria-tetanus-pertussis vaccination series
Assessment and comparison of anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates between infants born to mothers receiving TdaP2gen vaccine during pregnancy who are randomized to receive either aP- or wP-containing vaccines as the primary vaccination series during infancy
Time frame: Pre-primary series vaccination (within 2 months after birth) and post-primary series vaccination (at age 7 months +/- 14 days)
Phase 3: Infant anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates following booster diphtheria-tetanus-pertussis vaccination
Assessment and comparison of anti-PT, anti-FHA, anti-diphtheria toxoid, and anti-tetanus toxoid IgG geometric mean concentrations and seroresponse rates between infants born to mothers receiving TdaP2gen vaccine during pregnancy who previously received either aP or wP-containing vaccines during the primary vaccination series and subsequently receive booster vaccination at 15-18 months of age
Time frame: At 12 months of age (+/- 14 days), pre-booster vaccination, and 1 month after booster vaccination (+/- 14 days)
Phase 1: Maternal pertussis-neutralizing antibody geometric mean titers following TdaP2gen vaccination during pregnancy
Assessment of maternal pertussis-neutralizing antibody geometric mean titers in a subset of 40 pregnant women before TdaP2gen vaccination, after vaccination, and at delivery
Time frame: Pre-vaccination baseline, 4 weeks after vaccination (+/- 14 days), and at delivery
Phase 1: Cord blood pertussis-neutralizing antibody geometric mean titers at birth
Assessment of pertussis-neutralizing antibody geometric mean titers in cord blood samples from newborns of a subset of 40 vaccinated pregnant women at delivery
Time frame: At delivery
Phase 1: Knowledge and acceptability of pertussis and pertussis vaccine among pregnant women assessed using a structured questionnaire
Assessment of knowledge and acceptability of pertussis and pertussis vaccine among pregnant women using a structured questionnaire
Time frame: Pre-vaccination baseline
Phase 2: Infant pertussis-neutralizing antibody geometric mean titers following primary diphtheria-tetanus-pertussis vaccination series
Assessment and comparison of pertussis-neutralizing antibody geometric mean titers in a subset of 40 infants born to mothers receiving TdaP2gen vaccine during pregnancy who are randomized to receive either aP- or wP-containing vaccines as the primary vaccination series during infancy
Time frame: Pre-primary series vaccination (within 2 months after birth) and post-primary series vaccination (at age 7 months +/- 14 days)
Phase 2: Incidence of solicited local and systemic adverse events, unsolicited adverse events, and serious adverse events following the primary diphtheria-tetanus-pertussis vaccination series in infants
Assessment and comparison of the frequency and severity of solicited local and systemic adverse events, unsolicited adverse events, and serious adverse events following administration of aP- or wP-containing vaccines during the primary vaccination series in infants born to mothers receiving TdaP2gen vaccine during pregnancy
Time frame: From the first dose of the primary diphtheria-tetanus-pertussis vaccination series until 1 month after completion of the primary vaccination series, assessed up to approximately 5 months
Phase 3: Infant pertussis-neutralizing antibody geometric mean titers following booster diphtheria-tetanus-pertussis vaccination
Assessment and comparison of pertussis-neutralizing antibody geometric mean titers in a subset of 40 infants born to mothers receiving TdaP2gen vaccine during pregnancy who previously received either aP or wP-containing vaccines during the primary vaccination series and subsequently receive booster vaccination at 15-18 months of age
Time frame: At 12 months of age (+/- 14 days), pre-booster vaccination, and 1 month after booster vaccination (+/- 14 days)
Phase 3: Incidence of solicited local and systemic adverse events, unsolicited adverse events, and serious adverse events following booster diphtheria-tetanus-pertussis vaccination in infants
Assessment and comparison of the frequency and severity of solicited local and systemic adverse events, unsolicited adverse events, and serious adverse events following administration of aP or wP booster vaccination in infants born to mothers receiving TdaP2gen vaccine during pregnancy
Time frame: From booster vaccination through 28 days after vaccination
Plan to share: No — There is not a plan to make individual participant data (IPD) available for this study.
Start is estimated for May 2026; primary completion for Dec 2029, 43 months later.
Of 22 phase 4 interventional studies under Whooping Cough, half reached primary completion within 22 months of starting (the median), counting those still running; a quarter within 8 and three quarters within 34. This study's planned 43 months is above that.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in May 2026. You cannot join it, but the record below documents what was studied.
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