A Study to Learn How Safe, Tolerable and Capable of Producing an Immune Response is, a Modified RNA Vaccine Against Pandemic Influenza

February 19, 2026 updated by: Pfizer

A PHASE 1, RANDOMIZED, OBSERVER-BLIND, DOSE-RANGING STUDY TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF MODIFIED RNA VACCINE CANDIDATES AGAINST PANDEMIC INFLUENZA IN HEALTHY ADULTS

The purpose of this study is to learn about the safety and effects of the study vaccine for the possible prevention of influenza. Influenza is a disease that can spread easily from one person to another and cause body aches, fever, cough, and other symptoms. The study vaccine is called Pandemic Influenza modRNA (pdmFlu) Vaccine.

This study is seeking for participants who are:

  • between the ages of 18 to 49 years old or 65 to 84 years old.
  • willing and able to follow with all scheduled visits, treatment plan, laboratory tests, lifestyle changes, and other study procedures.
  • healthy as confirmed by medical history, physical examinations, and the study doctor.
  • capable of signing informed consent.

Participants will receive either:

  • the pdmFlu vaccine,
  • a licensed influenza vaccine
  • a placebo. A placebo does not have any medicine in it but looks just like the study medicine.

Participants will not know which vaccine they receive. Participants will receive the study vaccines as a single shot in the arm. The study will compare participant experiences to help understand if the pdmFlu vaccine is safe and effective. Participants will take part in this study for up to 13 months. During this time, the participants will receive the study vaccine and take part in follow-up visits.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

157

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Connecticut
      • New Haven, Connecticut, United States, 06511
        • Pfizer Clinical Research Unit - New Haven
    • Florida
      • Hollywood, Florida, United States, 33024
        • Research Centers of America
    • New York
      • New York, New York, United States, 10016
        • NYU Langone Health

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Key Inclusion Criteria:

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

Key Exclusion Criteria:

- Does not meet seasonal influenza vaccine requirements per cohort.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Sequential Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Placebo Comparator: Placebo
Biological: Placebo
Intramuscular injection
Active Comparator: Licensed influenza vaccine
Biological: Licensed influenza vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 1
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 2
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 3
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 4
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 5
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 6
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 7
Biological: pdmFlu vaccine
Intramuscular injection
Experimental: pdmFlu vaccine 8
Biological: pdmFlu vaccine
Intramuscular injection

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Percentage of participants by age group reporting local reactions
Time Frame: For 7 days after vaccination
For 7 days after vaccination
Percentage of participants by age group reporting systemic events
Time Frame: For 7 days after vaccination
For 7 days after vaccination
Percentage of participants by age group reporting adverse events
Time Frame: From vaccination to 4 weeks after each vaccination
From vaccination to 4 weeks after each vaccination
Percentage of participants by age group reporting serious adverse events
Time Frame: From vaccination to 6 months after last vaccination or through the last visit, whichever is longer
From vaccination to 6 months after last vaccination or through the last visit, whichever is longer
Percentage of participants by age group reporting medically attended adverse events
Time Frame: From vaccination to 6 months after last vaccination or through the last visit, whichever is longer
From vaccination to 6 months after last vaccination or through the last visit, whichever is longer
Percentage of participants by age group with abnormal hematology and chemistry laboratory values
Time Frame: 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
Percentage of participants by age group with grading shifts in hematology and chemistry laboratory assessments
Time Frame: Between baseline and 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
Between baseline and 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
Percentage of participants by age group with new clinically significant ECG abnormalities
Time Frame: 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
Percentage of participants by age group with new troponin I abnormalities
Time Frame: 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination
1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks after vaccination 1, 1 week and 4 weeks after vaccination 2, 1 week and 4 weeks after booster vaccination

Secondary Outcome Measures

Outcome Measure
Time Frame
Geometric mean titers (GMTs) of hemagglutination inhibition (HAI) titers
Time Frame: At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
Geometric mean fold rise (GMFR) in HAI titers from before vaccination to each subsequent timepoint
Time Frame: At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
Proportion of participants by age group achieving HAI seroconversion
Time Frame: At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
Proportion of participants by age group with HAI titer >=1:40
Time Frame: At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination
At baseline, 1 week, 3 weeks, 6 weeks, 8 weeks and 12 weeks, 16 weeks and 6 months after vaccination 1, 1 week, 4 weeks, 3 months and 6 months after vaccination 2, 1 week, 4 weeks, 12 weeks and 6 months after booster vaccination

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Pfizer

Investigators

  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 13, 2023

Primary Completion (Actual)

September 23, 2025

Study Completion (Actual)

September 23, 2025

Study Registration Dates

First Submitted

December 12, 2023

First Submitted That Met QC Criteria

December 12, 2023

First Posted (Actual)

December 21, 2023

Study Record Updates

Last Update Posted (Actual)

February 23, 2026

Last Update Submitted That Met QC Criteria

February 19, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • C5561001
  • NCT06179446 (Registry Identifier: ClinicalTrials.gov)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Influenza

Clinical Trials on Placebo

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Mauritius

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe