What is RSVpreF studying for RSV infection?

RSVpreF is being studied to understand its safety and how well it protects mothers and their babies when given during later pregnancies. Researchers aim to learn how long immunity lasts from a single dose given in a previous pregnancy. Pfizer is leading this clinical trial to help improve protection against RSV infection.

Who may be eligible for this RSV infection clinical trial?

Adults aged 18 to 49 who are pregnant between 24 and 36 weeks and expecting a single baby may be eligible. Participants must have received RSVpreF or Abrysvo vaccine in a prior pregnancy and not have any current pregnancy complications. Both women and nonpregnant adults previously vaccinated may join. Please review eligibility criteria for more details.

Is there any cost to participate in this RSV infection clinical trial?

Study-related care, including the study vaccine or placebo and all trial visits, is provided at no cost. Personal travel expenses may vary and are not guaranteed to be covered. Participants should plan accordingly for any travel or related costs.

Actively Recruiting

Phase 3

Age: 0Years +

All Genders

Healthy Volunteers

ID06866405

A Phase 3 Study to Investigate the Safety, Tolerability, and Immune Response of Revaccinating Pregnant Participants During Subsequent Pregnancies with a Bivalent RSV Vaccine

Led by Pfizer · Updated on 2026-06-05

550

Participants Needed

Research Sites

N/A

Total Duration

AI-Summary

What this Trial Is About

Researchers are studying the safety and immune response of giving a second dose of the RSVpreF vaccine during later pregnancies, as well as how long protection lasts from a single dose given in an earlier pregnancy. The study involves pregnant participants and their unborn babies, along with nonpregnant participants who received the vaccine before, to understand vaccine effects and immune duration. The trial is a Phase 3 study sponsored by Pfizer focused on respiratory syncytial virus (RSV) infection. The study includes three groups: Cohort 1 consists of pregnant participants who previously received RSVpreF in a Pfizer trial and will get a second dose; Cohort 2 includes pregnant participants who received RSVpreF commercially or in a prior trial, randomized to receive either RSVpreF or a placebo; Cohort 3 involves nonpregnant participants who had RSVpreF during a previous pregnancy and will provide blood samples to assess lasting immunity without receiving new vaccine doses. Infants born to vaccinated pregnant participants are monitored for safety and antibody levels for six months. Participants will attend visits for vaccinations, blood tests, and health monitoring. Pregnant participants are observed for reactions and side effects from the day of vaccination through weeks afterward. Infants are followed from birth up to six months to assess adverse events and antibody presence. The main outcomes include reports of vaccine reactions, adverse events, and the level of RSV antibodies at birth and up to six months. Nonpregnant participants provide blood samples to measure immune response persistence over time. The total study duration extends until February 2028.

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

Age: 0Years +

All Genders

Healthy Volunteers

Eligibility Criteria

You may qualify if you...

Women aged 18 to 49 who are pregnant between 24 and 36 weeks and expecting one baby without known risks for complications
Received RSVpreF or Abrysvo vaccine during a previous pregnancy
Had an ultrasound scan at 18 weeks or later in the current pregnancy showing no major fetal problems
Medically suitable to participate based on history and physical exam
Agrees to allow their baby to participate and provides consent
Able to sign informed consent
Nonpregnant adults who received RSVpreF during a previous pregnancy in a Pfizer trial and consent to participate

You will not qualify if you...

Received any approved or experimental RSV vaccine since their previous pregnancy
Pre-pregnancy body mass index over 40 kg/m2
History of severe allergic reaction to vaccines or vaccine ingredients
Current pregnancy problems at time of consent
Previous pregnancy problems at time of consent
Breastfeeding at enrollment
Participation in other drug trials within 28 days before consent or during the study period

AI-Screening

AI-Powered Screening

Complete this quick 3-step screening to check your eligibility

Your Study Journey

Screening

Duration - 2 to 4 weeks

Participants are screened for eligibility to participate in the trial.

1 visit (in-person)

Treatment

Duration - Single dose administered between 24 and 36 weeks of pregnancy

Pregnant participants receive a single dose of either the RSVpreF vaccine or a placebo during their pregnancy. Non-pregnant participants do not receive any vaccine but participate in immune response assessments.

1 vaccination visit (in-person)

Post-treatment Follow-up

Duration - Up to 6 months after birth for infants; up to 4 weeks after vaccination for pregnant participants

Participants are monitored for safety and immune response after vaccination. Infants born to vaccinated pregnant participants are monitored for safety and antibody levels for six months after birth.

Weekly visits for up to 4 weeks after vaccination for pregnant participants; approximately 6 infant visits over 6 months

Trial Site Locations

Total: 97 locations

Center for Research in Women's Health

Birmingham, Alabama, United States, 35233

Actively Recruiting

Children's of Alabama

Birmingham, Alabama, United States, 35233

Actively Recruiting

University of Alabama at Birmingham - School of Medicine

Birmingham, Alabama, United States, 35233

Actively Recruiting

University of Alabama at Birmingham Women & Infants Center

Birmingham, Alabama, United States, 35233

Actively Recruiting

USA Health Children's and Women's Hospital

Mobile, Alabama, United States, 36604

Actively Recruiting

USA Health Strada Patient Care Center

Mobile, Alabama, United States, 36604

Actively Recruiting

Ronald Reagan UCLA Medical Center

Los Angeles, California, United States, 90024

Actively Recruiting

Ronald Reagan UCLA Medical Center (inpatient hospital)

Los Angeles, California, United States, 90095

Actively Recruiting

Ronald Reagan UCLA Medical Center

Los Angeles, California, United States, 90095

Actively Recruiting

UCLA (outpatient clinic)

Los Angeles, California, United States, 90095

Actively Recruiting

UCLA Clinical and Translational Research Center (research clinic)

Los Angeles, California, United States, 90095

Actively Recruiting

UCLA

Los Angeles, California, United States, 90095

Actively Recruiting

Lucile Packard Children's Hospital-Labor and Delivery Unit

Palo Alto, California, United States, 94304

Actively Recruiting

Stanford Obstetrics Clinic

Palo Alto, California, United States, 94304

Actively Recruiting

Stanford University Medical Center

Palo Alto, California, United States, 94304

Actively Recruiting

Stanford University

Palo Alto, California, United States, 94304

Actively Recruiting

Anschutz Health Sciences Building (AHSB)