Actively Recruiting
Phase 3 Evaluation of Safety and Immune Response to a Second Dose of Bivalent RSV Vaccine During Pregnancy and Duration of Protection from a Previous Dose
Led by Pfizer · Updated on 2026-07-09
550
Participants Needed
97
Research Sites
N/A
Total Duration
On this page
AI-Summary
What this Trial Is About
Researchers are evaluating the safety and immune response of a second dose of the RSVpreF vaccine in pregnant women during later pregnancies. The study also aims to understand how long the protection lasts from a single dose given during a previous pregnancy by examining blood samples from nonpregnant participants who had the vaccine before. This Phase 3 trial involves pregnant participants and their unborn babies, as well as nonpregnant participants previously vaccinated. Pregnant participants are divided into two groups one group who previously received RSVpreF in a Pfizer trial will get a second dose, and another group will be randomly assigned to receive either RSVpreF or a placebo if no prior antibody data exists. Infants born to these participants will be followed for six months to monitor safety and antibody levels. Nonpregnant participants who received RSVpreF in an earlier trial will provide blood samples to assess the durability of their immune response without receiving additional vaccine doses. Participants will undergo safety monitoring including tracking local and systemic reactions, adverse events, and serious events during pregnancy and after birth for infants. Blood tests will measure neutralizing antibodies against RSV types A and B at birth, 3 months, and 6 months. The study includes consent procedures for both pregnant participants and infants, and nonpregnant participants will have scheduled visits for blood sample collection. The total study duration extends through infant follow-up and ongoing immune response assessments.
CONDITIONS
Brief Title
A Phase 3 Study of Revaccination in Subsequent Pregnancies With Bivalent RSV Vaccine and Duration of Protection of a Single Dose
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Women aged 18 to 49 who are pregnant between 24 and 36 weeks with a single baby without known risks
- Received RSVpreF or Abrysvo vaccine during a previous pregnancy
- Had an ultrasound scan at 18 weeks or later in current pregnancy with no major fetal problems
- Medically suitable based on history, physical exam, and doctor's judgment
- Willing to allow baby to participate and provide informed consent
- Able to sign consent form and agree to study conditions
- Nonpregnant participants who received one dose of RSVpreF during previous pregnancy in Pfizer trial and have prior results
- Able to sign consent form for study participation
You will not qualify if you...
- Received any approved or experimental RSV vaccine since previous pregnancy
- Pre-pregnancy body mass index over 40 kg/m2
- History of severe vaccine reaction or serious allergy to vaccine ingredients
- Current pregnancy problems or issues at consent
- Previous pregnancy problems at consent
- Breastfeeding at enrollment
- Participating in other drug studies within 28 days before consent or during study period
Research Team
P
Pfizer CT.gov Call Center
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