Comparative Immunologic Mechanisms and Microbiome Interactions Following Different Influenza Vaccine Formulations in Older Adults

NCT07805837 | Completed Phase 4 DMC

• 2 other identifiers: 2025GR0422RS-2025-00513707
• Study Type: interventional
• Target: 121
• Locations: 1 country
• Sites: 1

Brief 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. Additionally, the study investigates the role of the gut microbiome in modulating vaccine-induced immune responses and durability.

Conditions

Influenza; Influenza Vaccines; Microbiome; Immune Response

Keywords

Influenza, Influenza vaccines, Microbiome, Immune mechanism

Outcome Measures

Primary Outcomes (1)

• Seroconversion Rate

  ≥4-fold increase in hemagglutination inhibition (HI) antibody titers

  4 weeks post-vaccination

Secondary Outcomes (7)

• Geometric Mean Titers

  Baseline, Day 7, Week 4, Month 6

• Cellular Immune Responses

  Baseline, Day 7, Week 4

• B Cell Responses

  Baseline, Day 7, Week 4

• Microbiome Diversity and Composition

  Baseline and Week 4

• Microbiome Biomarker Identification

  Baseline, Week 4

Study Arms (3)

Standard-Dose Influenza Vaccine

ACTIVE COMPARATOR

Intervention: Standard-dose quadrivalent influenza vaccine (Vaxigrip®) Dose: 0.5 mL intramuscular injection, single dose

Biological: Standard-Dose Influenza Vaccine

MF59-Adjuvanted Influenza Vaccine

ACTIVE COMPARATOR

Intervention: MF59-adjuvanted vaccine (FLUAD®) Dose: 0.5 mL intramuscular injection, single dose

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

Biological: High-Dose Influenza Vaccine

Interventions

High-Dose Influenza Vaccine BIOLOGICAL

0.7 mL intramuscular injection, single dose

High-Dose Influenza Vaccine

Standard-Dose Influenza Vaccine BIOLOGICAL

0.5 mL intramuscular injection, single dose

Standard-Dose Influenza Vaccine

MF59-Adjuvanted Influenza Vaccine BIOLOGICAL

0.5 mL intramuscular injection, single dose

MF59-Adjuvanted Influenza Vaccine

Eligibility Criteria

• Age: 65 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Older Adult (65+)

You may qualify if:

• Age ≥65 years
• Able and willing to provide informed consent

You may not qualify if:

• Influenza vaccination within the past 6 months
• Laboratory-confirmed influenza infection within the past 6 months
• Immunocompromised status
• Uncontrolled chronic medical conditions

Sponsors & Collaborators

• Korea University Guro Hospital: lead

Study Sites (1)

Korea University Guro Hospital

Seoul, Seoul, 08308, South Korea

Location

MeSH Terms

Conditions

Influenza, Human

Interventions

Influenza Vaccines

Condition Hierarchy (Ancestors)

Respiratory Tract Infections; Infections; Orthomyxoviridae Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases

Intervention Hierarchy (Ancestors)

Viral Vaccines; Vaccines; Biological Products; Complex Mixtures

Study Officials

• Joon Young Song, MD, PhD

  Korea University Guro Hospital

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: phase 4
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Model Details: 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.

Study Record Dates

• First Submitted: September 1, 2026
• First Posted: September 4, 2026
• Study Start: October 25, 2025
• Primary Completion: January 31, 2026
• Study Completion: August 31, 2026
• Last Updated: September 4, 2026

Record last verified: 2025-10

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: Data will be available beginning 6 months following publication of the primary results and will remain available for 5 years.
• Access Criteria: Access to de-identified individual participant data and supporting documents will be provided to qualified researchers with a scientifically sound proposal. Requests will be reviewed and approved by the study investigators and the institutional review board. Data will be shared under a data use agreement to ensure participant confidentiality and compliance with applicable regulations.

Locations

KR (1)