Concurrent Versus Sequential Administration of Tdap and RSV Vaccines in Pregnancy

The goal of this clinical trial is to learn if the RSV vaccine (protects against respiratory syncytial virus) and Tdap vaccine (protects against pertussis) are most effective in pregnant individuals when taken together at the same visit, or separately at different visits. This clinical trial will also learn about the safety and immune responses of these vaccines in pregnancy. The Main question: -Is it possible to run a successful trial that tests how safe and effective it is to give Tdap and RSV vaccines in pregnancy either at the same time or one after the other, at different visits? The Secondary question: -To determine how safe and how well the Tdap and RSV vaccines work when given in pregnancy either at the same time or one after the other, at different visits. The Exploratory (optional participation) questions: * To measure the levels of antibodies against whooping cough (pertussis) and RSV in mothers at 7 and 19 months after giving birth, depending on whether they got the vaccines at the same time or one after the other during pregnancy. * To measure whooping cough antibody levels in the babies at 2, 7, and 19 months of age, whose mothers who received the vaccines in pregnancy. * To measure the levels of RSV antibodies in the mothers' breast milk at 1 week, 2 weeks, 4 weeks, and 2 months after giving birth. Participants will be randomly assigned to Group 1 (vaccines given at the same time, same visit) or Group 2 (vaccines given one after the other, at different visits). There are 4 visits as part of the main study, and 6 additional visits as part of the optional study (exploratory questions). Visit 1-2: Blood collection and vaccines administered Visit 3-4: Blood work (cord blood sample collection from infant, after delivery, if possible) Visit 5-8: Breast milk collection Visit 8-10: Blood collection (infant blood collection only at Visit 8). Participants will be asked to keep a diary of symptoms throughout the study.

NCT Number	NCT07097012
Lead Sponsor	Canadian Immunization Research Network Collaborators: Ottawa Hospital Research Institute, Vaccine Evaluation Center, Canada, University of British Columbia, Canadian Center for Vaccinology, Dalhousie University, IWK Health Centre, Public Health Agency of Canada (PHAC), Centre Hospitalier Univeritaire Sainte Justine
Conditions	RSV, Tdap - Tetanus, Diphtheria and Acellular Pertussis Vaccination, Pregnancy, Healthy
Enrollment	60 participants
Start Date	2025-10-16
Primary Completion	2026-07 (estimated)
Study Completion	2027-10 (estimated)
Updated on ClinicalTrials.gov	2026-06-16