Influenza Vaccine Immunogenicity in Repeatedly Vaccinated Older Adults

NCT07838298 | Recruiting Phase 4

• 2 other identifiers: 2026GR0376RS-2026-25468953
• Study Type: interventional
• Target: 180
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to compare immune responses to different influenza vaccine formulations in older adults and to understand how immune aging and repeated annual influenza vaccination affect these responses. The main questions it aims to answer are:

• Do standard dose, MF59 adjuvanted, and high dose influenza vaccines produce different immune responses in adults aged 65 years or older?
• How does immune aging affect responses to different influenza vaccine formulations?
• How do immune responses change with repeated annual influenza vaccination, and do these changes differ among vaccine formulations? Researchers will compare older adults who receive a standard dose, MF59 adjuvanted, or high dose influenza vaccine. Younger adults aged 19-49 years who receive a standard dose influenza vaccine will also be included as a reference group to help evaluate age related differences in immune responses. Participants will:
• Receive an influenza vaccine.
• Provide blood samples before and after vaccination to measure antibody and other immune responses.
• Some participants will provide additional blood or nasal samples for more detailed evaluation of immune responses.

Conditions

Influenza Vaccination; Older Adults (65 Years and Older); Immunosenescence; Immunogenicity; Repeated Vaccination

Outcome Measures

Primary Outcomes (2)

• Geometric mean titers of hemagglutination inhibition antibodies at 1 month after vaccination

  Geometric mean titers (GMTs) of hemagglutination inhibition antibodies against each influenza vaccine strain will be assessed at 1 month after vaccination.

  1 month after vaccination, annually for up to 3 years

• Geometric mean fold rise in hemagglutination inhibition antibody titers at 1 month after vaccination

  Geometric mean fold rises (GMFRs) in hemagglutination inhibition antibody titers from baseline to 1 month after vaccination will be assessed for each influenza vaccine strain.

  Baseline to 1 month after vaccination, annually for up to 3 years

Secondary Outcomes (4)

• Seroconversion rate following influenza vaccination

  Baseline and 1 month after vaccination, annually for up to 3 years

• Frequency of influenza specific B cells following vaccination

  Baseline, 1 week, and 1 month after vaccination, annually for up to 3 years

• normalized level of influenza specific secretory IgA in nasal samples

  1 month after vaccination in the first season; baseline and 1 month after vaccination annually in year 2 and 3

• Frequency of influenza specific T cells following vaccination

  Baseline, 1 week, and 1 month after vaccination, annually for up to 3 years

Other Outcomes (2)

• Molecular immune signatures associated with influenza vaccine responses

  Through study completion, up to 3 years

• Extracellular vesicle associated molecular signatures following influenza vaccination

  Through study completion, up to 3 years

Study Arms (4)

older adults- standard dose influenza vaccine

ACTIVE COMPARATOR

Biological: Standard dose influenza vaccine

older adults- adjuvanted influenza vaccine

EXPERIMENTAL

Biological: MF59 adjuvanted influenza vaccine

older adults- high dose influenza vaccine

EXPERIMENTAL

Biological: High dose influenza vaccine

younger adults- standard dose influenza vaccine

OTHER

Younger adults aged 19-49 years who receive a standard dose influenza vaccine and serve as a reference group for evaluating age related differences in immune responses

Biological: Standard dose influenza vaccine

Interventions

Standard dose influenza vaccine BIOLOGICAL

A single intramuscular dose of standard dose influenza vaccine administered according to the approved prescribing information.

older adults- standard dose influenza vaccine; younger adults- standard dose influenza vaccine

MF59 adjuvanted influenza vaccine BIOLOGICAL

A single intramuscular dose of MF59 adjuvanted influenza vaccine administered according to the approved prescribing information.

older adults- adjuvanted influenza vaccine

High dose influenza vaccine BIOLOGICAL

A single intramuscular dose of high dose influenza vaccine administered according to the approved prescribing information.

older adults- high dose influenza vaccine

Eligibility Criteria

• Age: 19 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Older adult group: aged 65 years or older
• Younger reference group: aged 19 to 49 years
• Able to receive influenza vaccination and complete the scheduled follow up

You may not qualify if:

• Receipt of an influenza vaccine or any other vaccine within 4 weeks prior to enrollment
• Immunocompromised status, including ongoing chemotherapy or immunosuppressive therapy, high dose corticosteroid therapy, history of solid organ or hematopoietic stem cell transplantation, active malignancy, HIV infection, or other clinically significant immunocompromising conditions
• Moderate or severe acute infection
• History of allergic reaction to an influenza vaccine or any of its components, or any other condition that precludes influenza vaccination
• Inability, as determined by the investigator, to understand the purpose and procedures of the study and provide voluntary informed consent

Sponsors & Collaborators

• Korea University Guro Hospital: lead
• National Research Foundation of Korea: collaborator

Study Sites (1)

Korea University Guro Hospital

Seoul, South Korea

RECRUITING

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

  STUDY CHAIR

Central Study Contacts

Min Joo Choi, MD, PhD

CONTACT

82-2-2626-3053; cowgow9696@gmail.com

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: Associated Professor

Study Record Dates

• First Submitted: September 13, 2026
• First Posted: September 24, 2026
• Study Start: September 21, 2026
• Primary Completion (Estimated): December 1, 2028
• Study Completion (Estimated): December 1, 2028
• Last Updated: September 24, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

KR (1)