InfluenzaPhase 4NCT07805837
Comparative Immunologic Mechanisms and Microbiome Interactions Following Different Influenza Vaccine Formulations in Older Adults
A Phase 4 study testing Standard-Dose Influenza Vaccine, MF59-Adjuvanted Influenza Vaccine and High-Dose Influenza Vaccine in people with Influenza and Influenza Vaccines, run by Korea University Guro Hospital at 1 site in South Korea.
Trial summary
This prospective, randomized, open-label clinical study aims to evaluate the immunogenicity and underlying immune mechanisms of different influenza vaccine formulations in adults aged ≥65 years. Read more about this study
- Who is it for?
- Ages 65 years and olderHealthy volunteers can take part
- Conditions the study is for
- Influenza, Influenza Vaccines, Microbiome
- What is being tested?
- Standard-Dose Influenza Vaccine, MF59-Adjuvanted Influenza Vaccine and High-Dose Influenza Vaccine
- Type of treatment
- Vaccines, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 121 participants
- Where
- 1 siteSouth Korea
- Study dates
- 25 Oct 2025to 31 Aug 2026
- Phase
- Phase 4
- Are there results?
- None posted in the registry
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 65 years and older
- All sexes
- Healthy volunteers accepted
- Older adult
Who may be able to join
- Age ≥65 years
- Able and willing to provide informed consent
Who cannot join
- Influenza vaccination within the past 6 months
- Laboratory-confirmed influenza infection within the past 6 months
- Immunocompromised status
- Uncontrolled chronic medical conditions
Trial locations and contacts
1 site in 1 country.
About this study
This prospective, randomized, open-label clinical study aims to evaluate the immunogenicity and underlying immune mechanisms of different influenza vaccine formulations in adults aged ≥65 years. Additionally, the study investigates the role of the gut microbiome in modulating vaccine-induced immune responses and durability.
Read the detailed description
Despite high influenza vaccination coverage among older adults in Korea, vaccine effectiveness remains suboptimal, even during well-matched seasons. Immunosenescence and microbiome dysbiosis are believed to contribute to reduced vaccine responsiveness.
This study will:
- Compare immune responses induced by standard-dose, MF59-adjuvanted, and high-dose influenza vaccines
- Characterize cellular and humoral immune mechanisms
- Analyze gut microbiome composition and function using metagenomic approaches
- Identify microbiome-derived biomarkers associated with vaccine responsiveness and durability
- Conditions
- Influenza, Influenza Vaccines, Microbiome, Immune Response
- Being tested
- Standard-Dose Influenza Vaccine, MF59-Adjuvanted Influenza Vaccine, High-Dose Influenza Vaccine
- Keywords
- Influenza, Influenza vaccines, Microbiome, Immune mechanism
- Medical subject headings
- Influenza, Human
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Standard-Dose Influenza VaccineBiological
0.5 mL intramuscular injection, single dose
MF59-Adjuvanted Influenza VaccineBiological
0.5 mL intramuscular injection, single dose
High-Dose Influenza VaccineBiological
0.7 mL intramuscular injection, single dose
| Study group | Role | What they receive |
|---|---|---|
| Standard-Dose Influenza Vaccine | Active comparator | Intervention: Standard-dose quadrivalent influenza vaccine (Vaxigrip®) Dose: 0.5 mL intramuscular injection, single dose Receives: Biological: Standard-Dose Influenza Vaccine |
| MF59-Adjuvanted Influenza Vaccine | Active comparator | Intervention: MF59-adjuvanted vaccine (FLUAD®) Dose: 0.5 mL intramuscular injection, single dose Receives: Biological: MF59-Adjuvanted Influenza Vaccine |
| High-Dose Influenza Vaccine | Active comparator | Intervention: High-dose influenza vaccine (Efluelda®) Dose: 0.7 mL intramuscular injection, single dose Receives: Biological: High-Dose Influenza Vaccine |
What is being measured
The primary outcome is the main question the study is designed to answer.
Seroconversion Rate
≥4-fold increase in hemagglutination inhibition (HI) antibody titers
Measured: 4 weeks post-vaccination
Secondary outcomes (7)
Geometric Mean Titers
Geometric Mean Titers (GMTs) of HI antibodies
Measured: Baseline, Day 7, Week 4, Month 6
Cellular Immune Responses
ELISpot (IFN-γ), activated T-cell frequency (CD38, HLA-DR)
Measured: Baseline, Day 7, Week 4
B Cell Responses
HA-specific B cell frequencies (A/H1N1, A/H3N2, B strains)
Measured: Baseline, Day 7, Week 4
Microbiome Diversity and Composition
Alpha diversity (Shannon index) Beta diversity (PERMANOVA)
Measured: Baseline and Week 4
Microbiome Biomarker Identification
Taxonomic and functional markers using LEfSe analysis
Measured: Baseline, Week 4
Durability of Immune Response
Antibody decay rate (half-life analysis)
Measured: Baseline, Week 4, Month 6
Safety Outcomes
Solicited adverse events (within 7 days) Unsolicited adverse events (within 30 days)
Measured: Day 7, Day 30
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Sep 2026
- Study start25 Oct 2025
- Primary completion31 Jan 2026
- Study completion31 Aug 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for InfluenzaStudies of the same condition, open and under way.
- 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 4
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- This study is a randomized, open-label, parallel-group clinical trial in which participants are assigned in a 1:1:1 ratio to receive one of three influenza vaccine formulations (standard-dose, MF59-adjuvanted, or high-dose). Each participant receives a single vaccine and is followed longitudinally for immunogenicity, safety, and microbiome analyses at predefined time points.
- Masking
- None (open label)
- Enrolment
- 121 participants (actual)
Sponsor and investigators
- Lead sponsor
- Korea University Guro Hospital
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Joon Young Song, Korea University Guro Hospital
- Investigators
- Joon Young Song, MD, PhD, Principal investigator, Korea University Guro Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07805837
- Sponsor's protocol ID
- 2025GR0422
- Other IDs
- RS-2025-00513707
- Status last verified
- Oct 2025
- First submitted
- 1 Sep 2026
- Last updated
- 4 Sep 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Individual participant data (IPD) that underlie the results reported in this study, after de-identification, will be made available to researchers upon reasonable request. Access will be granted following review and approval by the study investigators and institutional review board, in accordance with applicable regulations and data sharing policies.
Study at a glance
From the registry record, last updated by the sponsor on 4 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Comparative Immunologic Mechanisms and Microbiome Interactions Following Different Influenza Vaccine Formulations in Older Adults
- ClinicalTrials.gov ID
- NCT07805837
- Acronym / sponsor ID
- 2025GR0422
- Conditions
- Influenza, Influenza Vaccines, Microbiome, Immune Response
- Keywords
- Influenza, Influenza vaccines, Microbiome, Immune mechanism
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 121 participants (actual)
- Lead sponsor
- Korea University Guro HospitalUniversity, hospital or other
- Study start
- 25 Oct 2025 (actual)
- Primary completion
- 31 Jan 2026 (actual)
- Study completion
- 31 Aug 2026 (actual)
- First posted
- 4 Sep 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 prospective, randomized, open-label clinical study aims to evaluate the immunogenicity and underlying immune mechanisms of different influenza vaccine formulations in adults aged ≥65 years. Additionally, the study investigates the role of the gut microbiome in modulating vaccine-induced immune responses and durability.
Detailed description
Despite high influenza vaccination coverage among older adults in Korea, vaccine effectiveness remains suboptimal, even during well-matched seasons. Immunosenescence and microbiome dysbiosis are believed to contribute to reduced vaccine responsiveness.
This study will:
- Compare immune responses induced by standard-dose, MF59-adjuvanted, and high-dose influenza vaccines
- Characterize cellular and humoral immune mechanisms
- Analyze gut microbiome composition and function using metagenomic approaches
- Identify microbiome-derived biomarkers associated with vaccine responsiveness and durability
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 3
- Model description
- This study is a randomized, open-label, parallel-group clinical trial in which participants are assigned in a 1:1:1 ratio to receive one of three influenza vaccine formulations (standard-dose, MF59-adjuvanted, or high-dose). Each participant receives a single vaccine and is followed longitudinally for immunogenicity, safety, and microbiome analyses at predefined time points.
| Arm | Type | Receives |
|---|---|---|
| Standard-Dose Influenza Vaccine | Active comparator | Biological: Standard-Dose Influenza VaccineIntervention: Standard-dose quadrivalent influenza vaccine (Vaxigrip®) Dose: 0.5 mL intramuscular injection, single dose |
| MF59-Adjuvanted Influenza Vaccine | Active comparator | Biological: MF59-Adjuvanted Influenza VaccineIntervention: MF59-adjuvanted vaccine (FLUAD®) Dose: 0.5 mL intramuscular injection, single dose |
| High-Dose Influenza Vaccine | Active comparator | Biological: High-Dose Influenza VaccineIntervention: High-dose influenza vaccine (Efluelda®) Dose: 0.7 mL intramuscular injection, single dose |
Who may qualify
- Ages
- 65 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Older adult
Key inclusion criteria (2 listed)
- Age ≥65 years
- Able and willing to provide informed consent
Key exclusion criteria (4 listed)
- Influenza vaccination within the past 6 months
- Laboratory-confirmed influenza infection within the past 6 months
- Immunocompromised status
- Uncontrolled chronic medical conditions
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 |
|---|---|---|
| Standard-Dose Influenza Vaccine0.5 mL intramuscular injection, single dose | Biological | Standard-Dose Influenza Vaccine |
| MF59-Adjuvanted Influenza Vaccine0.5 mL intramuscular injection, single dose | Biological | MF59-Adjuvanted Influenza Vaccine |
| High-Dose Influenza Vaccine0.7 mL intramuscular injection, single dose | Biological | High-Dose Influenza Vaccine |
Primary outcome
Seroconversion Rate
Time frame: 4 weeks post-vaccination
≥4-fold increase in hemagglutination inhibition (HI) antibody titers
7 secondary outcomes
Geometric Mean Titers
Time frame: Baseline, Day 7, Week 4, Month 6
Cellular Immune Responses
Time frame: Baseline, Day 7, Week 4
B Cell Responses
Time frame: Baseline, Day 7, Week 4
Microbiome Diversity and Composition
Time frame: Baseline and Week 4
Microbiome Biomarker Identification
Time frame: Baseline, Week 4
Durability of Immune Response
Time frame: Baseline, Week 4, Month 6
Safety Outcomes
Time frame: Day 7, Day 30
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 4 Sep 2026.
- Individual participant dataSharing planned: Yes. Individual participant data (IPD) that underlie the results reported in this study, after de-identification, will be made available to researchers upon reasonable request. Access will be granted following review and approval by the study investigators and institutional review board, in accordance with applicable regulations and data sharing policies.
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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. This study is not recruiting at the moment.
Joon Young Song, MD, PhD principal investigator
Korea University Guro Hospital
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing Standard-Dose Influenza Vaccine, MF59-Adjuvanted Influenza Vaccine and High-Dose Influenza Vaccine in people with Influenza and Influenza Vaccines, run by Korea University Guro Hospital at 1 site in South Korea.
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 2 inclusion and 4 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: finished, as of the sponsor's last update on 4 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in South Korea. 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 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Seroconversion Rate (time frame: 4 weeks post-vaccination). 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 4 Sep 2026.