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Healthy AdultsPhase 2NCT07431853

A Study to Learn About mRNA Vaccines Against Influenza in Adults

A Phase 2 study testing Vaccine Candidate #1, Vaccine Candidate #2 and Vaccine Candidate #3 in people with Healthy Adults, run by Pfizer at 15 sites in United States.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

The purpose of this study is to learn about safety in participants taking the study vaccine (mRNA-based vaccine) and the ability of the study vaccine to trigger the body's immune response, targeting the flu virus (influenza virus). This study is seeking healthy participants 18 years of age or older. Read more about this study

Who is it for?
Ages 18 years and olderHealthy volunteers can take part
Conditions the study is for
Healthy Adults
What is being tested?
Vaccine Candidate #1, Vaccine Candidate #2 and Vaccine Candidate #3
Could I receive a placebo?
No, everyone receives an active treatment
How many people
770 participants
Where
15 sitesUnited States
Study dates
23 Feb 2026to 22 Jun 2027
Phase
Phase 2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • Healthy volunteers accepted
  • Adult, Older adult

Who may be able to join

  • Healthy and medically stable participants who are determined by medical history, physical examination (if clinically required), and clinical judgment of the investigator to be eligible for inclusion in the study.

Who cannot join

  • Tested positive for influenza ≤5 months (150 days) prior to Visit 1 (Day 1).
  • Vaccination with any investigational or licensed influenza vaccine ≤5 months (150 days) before Visit 1 (Day 1).
  • Receipt of antiviral therapies for influenza (eg, Tamiflu) ≤5 months (150 days) prior to Visit 1 (Day 1).

Trial locations and contacts

15 sites in 1 country. Contact the study team or a site near you to ask about taking part.

Pfizer CT.gov Call Center contact

1-800-718-1021

ClinicalTrials.gov_Inquiries@pfizer.com

15 sites in 1 country

United States15 sites, 15 recruiting

  • Charlottesville Medical Research Center, LLC

    Charlottesville, Virginia, 22911

    Recruiting

  • Indago Research & Health Center, Inc

    Hialeah, Florida, 33012

    Recruiting

  • East-West Medical Research Institute

    Honolulu, Hawaii, 96814

    Recruiting

  • AMR Clinical

    Kansas City, Missouri, 64114

    Recruiting

  • SMS Clinical Research LLC

    Mesquite, Texas, 75149

    Recruiting

  • Palm Springs Community Health Center

    Miami Lakes, Florida, 33014

    Recruiting

  • Clinical Research Consulting, LLC

    Milford, Connecticut, 06460

    Recruiting

  • AMR Clinical

    Mobile, Alabama, 36608

    Recruiting

  • DM Clinical Research - Philadelphia

    Philadelphia, Pennsylvania, 19107

    Recruiting

  • Rochester Clinical Research, LLC

    Rochester, New York, 14609

    Recruiting

  • J. Lewis Research, Inc. / Foothill Family Clinic

    Salt Lake City, Utah, 84109

    Recruiting

  • Clinical Research Atlanta

    Stockbridge, Georgia, 30281

    Recruiting

  • DM Clinical Research

    Tomball, Texas, 77375

    Recruiting

  • Diablo Clinical Research, LLC d/b/a Flourish Research

    Walnut Creek, California, 94598

    Recruiting

  • George Washington Medical Faculty Associates

    Washington D.C., District of Columbia, 20037

    Recruiting

Other trials in United States

About this study

Official title: A PHASE 2, RANDOMIZED, DOUBLE-BLIND, CLINICAL STUDY TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF MRNA VACCINES AGAINST INFLUENZA IN ADULTS 18 YEARS OF AGE AND OLDER

The purpose of this study is to learn about safety in participants taking the study vaccine (mRNA-based vaccine) and the ability of the study vaccine to trigger the body's immune response, targeting the flu virus (influenza virus).

This study is seeking healthy participants 18 years of age or older. All participants in this study will receive only 1 dose in their arm, to deliver one of the experimental flu vaccines or one of the approved flu vaccines used for comparison.

Participants will take part in this study for about 6 months, and participants will need to visit the study site at least 3 times. A blood sample will be taken at each of the 3 planned study visits and a swab from inside the nose will be taken at the first study visit.

Conditions
Healthy Adults
Being tested
Vaccine Candidate #1, Vaccine Candidate #2, Vaccine Candidate #3, Vaccine Candidate #4, Vaccine Candidate #5
Keywords
Influenza vaccination
Medical subject headings
Influenza, Human

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Vaccine Candidate #1Biological

    Investigational influenza Vaccine

  • Vaccine Candidate #2Biological

    Investigational influenza Vaccine

  • Vaccine Candidate #3Biological

    Investigational Influenza Vaccine

  • Vaccine Candidate #4Biological

    Investigational Influenza Vaccine

  • Vaccine Candidate #5Biological

    Investigational Influenza Vaccine

  • Vaccine Candidate #6Biological

    Investigational Influenza Vaccine

  • TIV1 or TIV2Biological

    Licensed influenza vaccine

Study groups in NCT07431853
Study groupRoleWhat they receive
AExperimentalmRNA influenza vaccine candidate #1 as a single intramuscular (IM) injection on Day 1.
Receives: Biological: Vaccine Candidate #1
BExperimentalmRNA influenza vaccine candidate #2 as a single IM injection on Day 1.
Receives: Biological: Vaccine Candidate #2
CExperimentalmRNA influenza vaccine candidate #3 as a single IM injection on Day 1.
Receives: Biological: Vaccine Candidate #3
DExperimentalmRNA influenza vaccine candidate #4 as a single IM injection on Day 1.
Receives: Biological: Vaccine Candidate #4
EExperimentalmRNA influenza vaccine candidate #5 as a single IM injection on Day 1.
Receives: Biological: Vaccine Candidate #5
FExperimentalmRNA influenza vaccine candidate #6 as a single IM injection on Day 1.
Receives: Biological: Vaccine Candidate #6
GActive comparatorLicensed influenza vaccine (TIV1 or TIV2) as a single IM injection.
Receives: Biological: TIV1 or TIV2

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Percentage of participants reporting prespecified local reactions following vaccination

    Measured: Within 7 days after vaccination

  2. Percentage of participants reporting prespecified systemic events following vaccination.

    Measured: Within 7 days after vaccination

  3. Percentage of participants reporting adverse events (AEs) following vaccination.

    Measured: Within 1 month after vaccination

  4. Percentage of participants reporting serious adverse events (SAEs) following vaccination.

    Measured: Within 6 months after vaccination

  5. Percentage of participants reporting newly diagnosed chronic medical conditions (NDCMCs) following vaccination.

    Measured: Within 6 months after vaccination

Secondary outcomes (3)

  1. Geometric Mean Titer (GMT) of Anti-Influenza Antibody Levels to each of the influenza antigens of the vaccine.

    Measured: Before vaccination and at 4 weeks after vaccination

  2. Geometric Mean Fold Rise (GMFR) of Anti-Influenza Antibody Levels to each of the influenza antigens of the vaccine

    Measured: Before vaccination to 4 weeks after vaccination

  3. Percentage of participants with satisfactory antibody response to the vaccine.

    Measured: Before vaccination to 4 weeks after vaccination

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted25 Feb 2026
  2. Study start23 Feb 2026
  3. Primary completion22 Jun 2027 (estimated)
  4. Study completion22 Jun 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2
Primary purpose
Prevention
Allocation
Randomised
Intervention model
Parallel groups
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
770 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07431853
Sponsor's protocol ID
C6481001
Status last verified
May 2026
First submitted
19 Feb 2026
Last updated
6 May 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Vaccine Candidate #1, Vaccine Candidate #2 and Vaccine Candidate #3 in people with Healthy Adults, run by Pfizer at 15 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 1 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 6 May 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 15 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Pfizer CT.gov Call Center (1-800-718-1021, ClinicalTrials.gov_Inquiries@pfizer.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Percentage of participants reporting prespecified local reactions following vaccination (time frame: Within 7 days after vaccination). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07431853.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 May 2026; AzTrials last refreshed its copy on 7 Nov 2026.

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