NCT06866405 · Pfizer
A Phase 3 Study of Revaccination in Subsequent Pregnancies With Bivalent RSV Vaccine and Duration of Protection of a Single Dose
What this study is about
This study aims to check how safe and well-tolerated a second dose of RSVpreF is when given during later pregnancies, and to see how long the immunity lasts from a single dose given during a previous pregnancy by examining the blood of nonpregnant participants who had the vaccine before.
View original scientific description
This study aims to check how safe and well-tolerated a second dose of RSVpreF is when given during later pregnancies, and to see how long the immunity lasts from a single dose given during a previous pregnancy by examining the blood of nonpregnant participants who had the vaccine before.
Interventions
BIOLOGICAL
RSVpreF
Single Dose
BIOLOGICAL
Placebo
Single Dose
Primary outcome measures
Percentage of pregnant participants reporting local reactions
Time frame: From Day 1 Through at least Day 7 after Vaccination
Pain at the injection site, redness, and swelling
Percentage of pregnant participants reporting systemic events
Time frame: From Day 1 Through at least Day 7 after Vaccination
Fever, fatigue, headache, vomiting, nausea, diarrhea, muscle pain, and joint pain
Percentage of pregnant participants reporting adverse events
Time frame: From Day 1 through 4 weeks after vaccination
Percentage of pregnant participants reporting serious adverse events
Time frame: From Day 1 throughout the study
In infant participants born to pregnant participants receiving a second dose of the study intervention, the percentage of participants reporting adverse events.
Time frame: From birth through 1 month of age
In infant participants born to pregnant participants receiving a second dose of the study intervention, the percentage of participants reporting serious adverse events and newly diagnosed medical conditions.
Time frame: From birth through 6 months of age.
Proportion of participants achieving neutralizing antibody to RSV A and RSV B at birth
Time frame: At birth
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
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
Where
- Birmingham, Alabama
- Mobile, Alabama
- Los Angeles, California
- Palo Alto, California
- Aurora, Colorado
- North Miami Beach, Florida
- Panama City, Florida
- Boise, Idaho
- Idaho Falls, Idaho
- Nampa, Idaho
- Ames, Iowa
- Kansas City, Kansas
And 20 more locations — see the full list below.
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Jul 9, 2026 · Source of record for eligibility and locations