A Phase 3 Study of Revaccination in Subsequent Pregnancies With Bivalent RSV Vaccine and Duration of Protection of a Single Dose

Launched by PFIZER · Mar 4, 2025

Keywords

ClinConnect Summary

This clinical trial is studying the safety and effectiveness of giving a second dose of the RSVpreF vaccine to pregnant women during later pregnancies. RSV (respiratory syncytial virus) can cause serious respiratory infections, especially in infants. The researchers want to find out how well a single dose of the vaccine works over time and if a second dose is safe for mothers and their babies. The trial will involve pregnant women between 24 and 36 weeks along who have received the RSV vaccine during a previous pregnancy and have no known complications in their current pregnancy.

To participate, women must be between 18 and 49 years old and meet specific health criteria, like having a normal ultrasound and not having received any other RSV vaccines since their last pregnancy. Participants will be asked to provide consent for both themselves and their babies to take part in the study. There will also be a group of nonpregnant individuals who had received the vaccine in a previous trial, helping the researchers understand how long the immunity lasts. Overall, participants can expect close monitoring and follow-up visits to ensure their safety and the effectiveness of the vaccine throughout the study.

Gender

ALL

Eligibility criteria

• • Pregnant Participants-Cohort 1 and Cohort 2 Key Inclusion Criteria
• • Women aged 18 to 49 who are pregnant, between 24 and 36 weeks along, and expecting one baby without known risks for complications can participate.
• • Had the RSVpreF or Abrysvo vaccine during a previous pregnancy.
• • Had an ultrasound scan at 18 weeks or later during their current pregnancy, with no major fetal problems detected.
• • Based on their medical history, physical check-up, and the doctor's judgment, they are found suitable to join the study.
• • Agrees to let their baby take part in the study and gives their permission.
• • Able to sign a consent form, agreeing to follow the rules and conditions of the study.
• • Key Exclusion Criteria
• • Received any approved or experimental RSV vaccine since their previous pregnancy.
• • Has a pre-pregnancy body mass index (BMI) over 40 kg/m2.
• • History of a severe bad reaction to a vaccine or a serious allergic reaction (like anaphylaxis) to any ingredient in the study vaccine or a similar vaccine.
• • Current pregnancy problems or issues at the time of giving consent.
• • Previous pregnancy issues or problems at the time of giving consent.
• • Infant Participants
• • Proof that the parent(s) or legal guardian(s) has signed and dated a consent form.
• • Parent(s) or legal guardian(s) must agree to attend scheduled visits and follow the study plan, including laboratory tests and other procedures.
• • Nonpregnant Participants-Cohort 3 Key Inclusion Criteria
• • Have already received one dose of the RSVpreF vaccine during their previous pregnancy as part of the Pfizer clinical trial, and the results from that time can be used for this study.
• • Able to sign a consent form, agreeing to follow the rules and requirements of the study.
• • Key Exclusion Criteria
• • Received any approved or experimental RSV vaccine after participating in the Pfizer clinical trial.
• • Taking part in other studies with new drugs within 28 days before giving consent or during the study period.