Influenza, HumanPhase 3NCT07851246
A Study to Evaluate the Immune Response and Safety of a Vaccine Against Influenza in Adults 18-64 Years of Age
A Phase 3 study testing mRNA Seasonal Flu vaccine, Comparator 1 and Comparator 2 in people with Influenza, Human, run by GlaxoSmithKline at 12 sites in United States.
Trial summary
This clinical trial will study an investigational seasonal influenza vaccine in adults 18 to 64 years of age. The vaccine is based on messenger ribonucleic acid, also called mRNA. Read more about this study
- Who is it for?
- Ages 18 to 64 yearsHealthy volunteers can take part
- Conditions the study is for
- Influenza, Human
- What is being tested?
- mRNA Seasonal Flu vaccine, Comparator 1 and Comparator 2
- Type of treatment
- Vaccines, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 3,000 participants
- Where
- 12 sitesUnited States
- Study dates
- 1 Oct 2026to 9 Jul 2027
- Phase
- Phase 3
- 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 to 64 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Participants who, in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g., completion of the eDiary, return for follow-up visits, attendance to study contacts, and ability to access and utilize a phone or other electronic communications) independently or with the assistance of a caregiver.
- A male or female participant between and including 18 to 64 years of age at the time of study intervention administration
- Participants of childbearing potential may be enrolled, if the participant:
- has practiced adequate contraception for at least 30 days prior to study intervention administration, and
- has a negative urine pregnancy test within 24 hours prior to study intervention administration, and
- has agreed to continue adequate contraception for at least 8 weeks after study intervention administration.
Who cannot join
- History of test confirmed influenza infection within 180 days prior to study intervention administration.
- Confirmed or suspected immunosuppressive or immunodeficient condition, except for stable human immunodeficiency virus infection meeting protocol-defined stability criteria.
- History of myocarditis or pericarditis considered causally associated with the administration of an mRNA vaccine.
- History of hypersensitivity or allergic reaction to any previous influenza vaccine.
- History of hypersensitivity or allergic reaction to any previous mRNA vaccine.
- History of Guillain-Barré syndrome (GBS) within 6 weeks of receiving any vaccine.
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- Acute or unstable chronic conditions as determined by medical history and clinical examination.
- Administration of an influenza vaccine in the period starting 180 days before the study intervention administration or planned administration prior to Visit 2 during the study.
- Planned administration/administration of prohibited vaccines within protocol-defined time windows before or after study intervention administration.
- Use of any investigational or non-registered product (other than the study intervention during the period beginning 30 days before the dose of study intervention (Day -29 to Day 1), or their planned use during the study period.
- Chronic administration of immune-modifying drugs (defined as more than 14 consecutive days in total) and/or planned use of long-acting immune modifying treatments at any time up to the end of the study.
- Pregnant or lactating female participant.
Trial locations and contacts
12 sites in 1 country. Contact the study team or a site near you to ask about taking part.
12 sites in 1 country
United States12 sites, 12 recruiting
- Recruiting
GSK Investigational Site
DeSoto, Texas, 75115
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Fort Worth, Texas, 76135
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Glendale, Arizona, 85308
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Hartsdale, New York, 10530
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Lenexa, Kansas, 66219
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Meridian, Idaho, 83642-3154
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Miami, Florida, 33186
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Miami Lakes, Florida, 33016
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
San Diego, California, 92123
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Spartanburg, South Carolina, 29303
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Tucson, Arizona, 85711
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
- Recruiting
GSK Investigational Site
Valparaiso, Indiana, 46383
US GSK Clinical Trials Call Center, 877-379-3718, GSKClinicalSupportHD@gsk.com
EU GSK Clinical Trials Call Centre, +44 (0) 20 8990 4466, GSKClinicalSupportHD@gsk.com
About this study
Official title: A Phase 3 Randomized, Observer-Blind, Controlled Study to Evaluate the Immunogenicity, Reactogenicity and Safety of an mRNA-based Seasonal Influenza Vaccine, in Adults 18-64 Years of Age
This clinical trial will study an investigational seasonal influenza vaccine in adults 18 to 64 years of age. The vaccine is based on messenger ribonucleic acid, also called mRNA. The main goals of the study are to learn how well the vaccine helps the body make an immune response against influenza and what medical problems participants may have after vaccination. Researchers will also compare immune responses in adults 18 to 64 years of age from this study, with immune responses in adults 65 years of age and older from another study. Participants will receive 1 injection into the upper arm muscle and will be followed for about 6 months.
- Conditions
- Influenza, Human
- Being tested
- mRNA Seasonal Flu vaccine, Comparator 1, Comparator 2
- Keywords
- Influenza;, Seasonal influenza vaccine;, Messenger ribonucleic acid vaccine;, mRNA vaccine;, Immunogenicity;, Reactogenicity;, Safety
- Medical subject headings
- Influenza, Human
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
mRNA Seasonal Flu vaccineBiological
One dose of the mRNA Flu vaccine received intramuscularly.
Comparator 1Biological
One dose of the comparator vaccine received intramuscularly.
Comparator 2Biological
One dose of the comparator vaccine received intramuscularly.
| Study group | Role | What they receive |
|---|---|---|
| mRNA Seasonal Flu Vaccine - Cohort 1 | Experimental | Participants 18 to 64 years of age will receive a single dose of investigational mRNA Seasonal Flu vaccine on Day 1. Receives: Biological: mRNA Seasonal Flu vaccine |
| Comparator 1_Cohort 1 | Active comparator | Participants 18 to 64 years of age will receive a single dose of comparator 1 on Day 1. Receives: Biological: Comparator 1 |
| mRNA Seasonal Flu Vaccine - Cohort 2 | Experimental | Participants 60 to 64 years of age will receive a single dose of investigational mRNA Seasonal Flu vaccine on Day 1. Receives: Biological: mRNA Seasonal Flu vaccine |
| Comparator 2_Cohort 2 | Active comparator | Participants 60 to 64 years of age will receive a single dose of comparator 2 on Day 1. Receives: Biological: Comparator 2 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Geometric Mean Titer (GMT) of Antigen 1 Titer
Measured: At Day 29
GMT of Antigen 2 Titer
Measured: At Day 29
Percentage of participants with Antigen 1 seroconversion rate (SCR)
Measured: From Day 1 to Day 29
Number of participants with solicited administration site adverse events
Measured: Day 1 to Day 7
Number of participants with systemic adverse events
Measured: Day 1 to Day 7
Number of participants with unsolicited adverse events
Measured: Day 1 to Day 28
Number of participants with serious adverse events (SAEs)
Measured: Day 1 to Day 181
Number of participants with adverse events of special interest (AESIs)
Measured: Day 1 to Day 181
Number of Participants with any Laboratory abnormalities
Measured: At Day 1 (pre-dose) and at Day 29 (post - dose)
Secondary outcomes (9)
GMT of Antigen 1 and Antigen 2 antibodies
Measured: At Day 29
Percentage of Participants with Antigen 1 and Antigen 2 antibodies SCR
Measured: Day 1 to Day 29
Geometric Mean Increase (GMI) of Antigen 1 Titer
Measured: At Day 29 relative to baseline (Day 1)
GMI of Antigen 2 Titer
Measured: At Day 29 relative to baseline (Day 1)
Percentage of Participants with Antigen 1 Seroprotection Rate (SPR)
Measured: At Day 1 and Day 29
Percentage of Participants with Antigen 2 SCR
Measured: Day 1 to Day 29
GMT of virus neutralization titers
Measured: At Day 29
Percentage of participants with seroconversion of virus neutralization titers
Measured: Day 1 to Day 29
GMI of virus neutralization titers
Measured: At Day 29 relative to baseline (Day 1)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted1 Oct 2026
- Study start1 Oct 2026
- Primary completion9 Jul 2027 (estimated)
- Study completion9 Jul 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Influenza, HumanStudies of the same condition, open and under way.
- More trials run by GlaxoSmithKlineThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
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 3
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 3,000 participants (estimated)
Sponsor and investigators
- Lead sponsor
- GlaxoSmithKline
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07851246
- Sponsor's protocol ID
- 218132
- Other IDs
- 2026-526925-17
- Status last verified
- Oct 2026
- First submitted
- 25 Sep 2026
- Last updated
- 9 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/gsk-patient-level-data-sharing-july2025.pdf
Study at a glance
From the registry record, last updated by the sponsor on 9 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 3 Randomized, Observer-Blind, Controlled Study to Evaluate the Immunogenicity, Reactogenicity and Safety of an mRNA-based Seasonal Influenza Vaccine, in Adults 18-64 Years of Age
- ClinicalTrials.gov ID
- NCT07851246
- Acronym / sponsor ID
- 218132
- Conditions
- Influenza, Human
- Keywords
- Influenza;, Seasonal influenza vaccine;, Messenger ribonucleic acid vaccine;, mRNA vaccine;, Immunogenicity;, Reactogenicity;, Safety
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 3,000 participants (estimated)
- Lead sponsor
- GlaxoSmithKlineIndustry (pharma, biotech, devices)
- Study start
- 1 Oct 2026 (actual)
- Primary completion
- 9 Jul 2027 (estimated)
- Study completion
- 9 Jul 2027 (estimated)
- First posted
- 1 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This clinical trial will study an investigational seasonal influenza vaccine in adults 18 to 64 years of age. The vaccine is based on messenger ribonucleic acid, also called mRNA. The main goals of the study are to learn how well the vaccine helps the body make an immune response against influenza and what medical problems participants may have after vaccination. Researchers will also compare immune responses in adults 18 to 64 years of age from this study, with immune responses in adults 65 years of age and older from another study. Participants will receive 1 injection into the upper arm muscle and will be followed for about 6 months.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| mRNA Seasonal Flu Vaccine - Cohort 1 | Experimental | Biological: mRNA Seasonal Flu vaccineParticipants 18 to 64 years of age will receive a single dose of investigational mRNA Seasonal Flu vaccine on Day 1. |
| Comparator 1_Cohort 1 | Active comparator | Biological: Comparator 1Participants 18 to 64 years of age will receive a single dose of comparator 1 on Day 1. |
| mRNA Seasonal Flu Vaccine - Cohort 2 | Experimental | Biological: mRNA Seasonal Flu vaccineParticipants 60 to 64 years of age will receive a single dose of investigational mRNA Seasonal Flu vaccine on Day 1. |
| Comparator 2_Cohort 2 | Active comparator | Biological: Comparator 2Participants 60 to 64 years of age will receive a single dose of comparator 2 on Day 1. |
Who may qualify
- Ages
- 18 to 64 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- Participants who, in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g., completion of the eDiary, return for follow-up visits, attendance to study contacts, and ability to access and utilize a phone or other electronic communications) independently or with the assistance of a caregiver.
- A male or female participant between and including 18 to 64 years of age at the time of study intervention administration
- Participants of childbearing potential may be enrolled, if the participant:
Key exclusion criteria (12 listed)
- History of test confirmed influenza infection within 180 days prior to study intervention administration.
- Confirmed or suspected immunosuppressive or immunodeficient condition, except for stable human immunodeficiency virus infection meeting protocol-defined stability criteria.
- History of myocarditis or pericarditis considered causally associated with the administration of an mRNA vaccine.
- History of hypersensitivity or allergic reaction to any previous influenza vaccine.
- History of hypersensitivity or allergic reaction to any previous mRNA vaccine.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| mRNA Seasonal Flu vaccineOne dose of the mRNA Flu vaccine received intramuscularly. | Biological | mRNA Seasonal Flu Vaccine - Cohort 1, mRNA Seasonal Flu Vaccine - Cohort 2 |
| Comparator 1One dose of the comparator vaccine received intramuscularly. | Biological | Comparator 1_Cohort 1 |
| Comparator 2One dose of the comparator vaccine received intramuscularly. | Biological | Comparator 2_Cohort 2 |
Primary outcome
Geometric Mean Titer (GMT) of Antigen 1 Titer
Time frame: At Day 29
GMT of Antigen 2 Titer
Time frame: At Day 29
Percentage of participants with Antigen 1 seroconversion rate (SCR)
Time frame: From Day 1 to Day 29
Number of participants with solicited administration site adverse events
Time frame: Day 1 to Day 7
Number of participants with systemic adverse events
Time frame: Day 1 to Day 7
Number of participants with unsolicited adverse events
Time frame: Day 1 to Day 28
Number of participants with serious adverse events (SAEs)
Time frame: Day 1 to Day 181
Number of participants with adverse events of special interest (AESIs)
Time frame: Day 1 to Day 181
Number of Participants with any Laboratory abnormalities
Time frame: At Day 1 (pre-dose) and at Day 29 (post - dose)
9 secondary outcomes
GMT of Antigen 1 and Antigen 2 antibodies
Time frame: At Day 29
Percentage of Participants with Antigen 1 and Antigen 2 antibodies SCR
Time frame: Day 1 to Day 29
Geometric Mean Increase (GMI) of Antigen 1 Titer
Time frame: At Day 29 relative to baseline (Day 1)
GMI of Antigen 2 Titer
Time frame: At Day 29 relative to baseline (Day 1)
Percentage of Participants with Antigen 1 Seroprotection Rate (SPR)
Time frame: At Day 1 and Day 29
Percentage of Participants with Antigen 2 SCR
Time frame: Day 1 to Day 29
GMT of virus neutralization titers
Time frame: At Day 29
Percentage of participants with seroconversion of virus neutralization titers
Time frame: Day 1 to Day 29
GMI of virus neutralization titers
Time frame: At Day 29 relative to baseline (Day 1)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 9 Oct 2026.
- Individual participant dataSharing planned: Yes. Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/gsk-patient-level-data-sharing-july2025.pdf
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
12 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing mRNA Seasonal Flu vaccine, Comparator 1 and Comparator 2 in people with Influenza, Human, run by GlaxoSmithKline at 12 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 6 inclusion and 12 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 9 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 12 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 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
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 US GSK Clinical Trials Call Center (877-379-3718, GSKClinicalSupportHD@gsk.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Geometric Mean Titer (GMT) of Antigen 1 Titer (time frame: At Day 29). The study lists 9 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 9 Oct 2026; AzTrials last refreshed its copy on 26 Oct 2026.