A Study on the Immune Response and Safety of a Combined Vaccine Against Diphtheria, Tetanus and Acellular Pertussis (dTpa) in Japanese Healthy Pregnant Women

The purpose of this Phase 3, non-randomized, single-arm, open-label study is to evaluate the immune response, reactogenicity and safety of GSKs dTpa vaccine in Japanese pregnant women between 27 weeks and less than 37 weeks of pregnancy. Both the pregnant women and their neonates born during the study will be evaluated for specific analyses.

Inclusion Criteria: 1. Participants, who, in the opinion of the investigator, can and will comply with the requirements of the protocol. 2. Participants and Legally acceptable representative(s) \[LAR(s)\] who give physical or digital informed consent after the study has been explained according to local regulatory requirements, and before any study-specific procedures are performed. The informed consent given at screening should include consent for both the maternal participant's participation and participation of the infant after the infant's birth. 3. Healthy participants as established by medical history and clinical examination at screening. 4. Participants between and including 18 and 45 years of age at the time of the study intervention administration (Visit 1/Day 1). 5. Pre-pregnancy body mass index (BMI) (based on participant's report) between 17.0 and 39.9 kg/m\^2, inclusive. 6. Pregnant female at 27,0/7 to 36,6/7 weeks of gestation (completed week 27 but not week 37) at the time of vaccination (Visit 1/Day 1), as established or confirmed by ultrasound examination. 7. No significant fetal abnormalities, as observed by the fetal morphological abnormality screening test conducted after 18 weeks of gestation and the most recent ultrasound testing (no more than 6 weeks before enrollment). 8. Nuchal translucency scan, serum testing and any other prenatal tests, if conducted, should suggest normal pregnancy. 9. Participants who are willing to provide cord blood and/or infant blood. 10. Participants who are willing to have them and their newborns followed-up until 1 month post-delivery. 11. Participants who do not plan to give their child for adoption. 12. Japanese ethnic origin. Exclusion Criteria: Medical conditions: 1. Participants diagnosed with multiple pregnancies. 2. Women with co-morbid medical or obstetric conditions that in the opinion of the investigator have the potential to complicate the pregnancy course and outcomes such as; * Gestational hypertension (defined as systolic blood pressure \>=140 mmHg and/or diastolic blood pressure \>=90 mmHg) at \>=20 weeks of gestation in a woman with a previously normal blood pressure. Women with gestational hypertension who maintain blood pressure in the normal range (\