RecruitingPhase 2

A Study to Learn About mRNA Vaccines Against Influenza in Adults

United States770 participantsStarted 2026-02-23

Plain-language 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. 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.

Who can participate

Age range

18 Years

Sex

ALL

See this in plain English?

AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.

Inclusion Criteria • 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. Exclusion Criteria * 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).

Questions worth asking your doctor

Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.

1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?

Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.

Questions for the trial coordinator

The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.

1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?

A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.

What they're measuring

Percentage of participants reporting prespecified local reactions following vaccination

Timeframe: Within 7 days after vaccination

Percentage of participants reporting prespecified systemic events following vaccination.

Timeframe: Within 7 days after vaccination

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

Timeframe: Within 1 month after vaccination

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

Timeframe: Within 6 months after vaccination

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

Timeframe: Within 6 months after vaccination

Trial details

NCT IDNCT07431853

SponsorPfizer

Sponsor typeINDUSTRY

Study typeINTERVENTIONAL

Primary completion2027-06-22

Contact for this trial

Pfizer CT.gov Call Center

1-800-718-1021 ClinicalTrials.gov_Inquiries@pfizer.com

View on ClinicalTrials.gov More Healthy Adults trials

Plain-language summary

Who can participate

Age range

18 Years

Sex

ALL

See this in plain English?

AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.

What they're measuring

Percentage of participants reporting prespecified local reactions following vaccination

Timeframe: Within 7 days after vaccination

Percentage of participants reporting prespecified systemic events following vaccination.

Timeframe: Within 7 days after vaccination

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

Timeframe: Within 1 month after vaccination

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

Timeframe: Within 6 months after vaccination

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

Timeframe: Within 6 months after vaccination