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NCT Number: NCT07838298

Influenza Vaccine Immunogenicity in Repeatedly Vaccinated Older Adults

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.

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Key information

Conditions

Influenza Vaccination Immunogenicity Immunosenescence Infections Influenza, Human Older Adults (65 Years and Older) Orthomyxoviridae Infections RNA Virus Infections Repeated Vaccination Respiratory Tract Diseases Respiratory Tract Infections Virus Diseases

Age range

19 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 4

Primary location

Korea University Guro Hospital

Seoul, South Korea

Location status: Recruiting

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 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

Exclusion criteria

  • 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

Treatment and study plan

Standard Dose Influenza vaccine

Biological

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

MF59 adjuvanted influenza vaccine

Biological

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

High Dose Influenza vaccine

Biological

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

Primary outcomes

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

    Time frame: 1 month after vaccination, annually for up to 3 years

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

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

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

    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.

Secondary outcomes

  1. Seroconversion rate following influenza vaccination

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

    The proportion of participants achieving a prespecified serologic response, defined as a fourfold or greater increase in hemagglutination inhibition antibody titer from baseline, will be assessed for each vaccine strain.

  2. Frequency of influenza specific B cells following vaccination

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

    The frequency of influenza specific B cells will be assessed at baseline, 1 week, and 1 month after vaccination. Responses will be compared among vaccine formulations and evaluated according to age and repeated annual vaccination.

  3. normalized level of influenza specific secretory IgA in nasal samples

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

    Influenza specific secretory IgA will be measured in nasal samples and normalized to total protein concentration measured using the BCA assay. Normalized secretory IgA levels will be used to assess mucosal immune responses. A pilot assessment will be conducted during the first vaccination season, followed by assessment before and 1 month after vaccination during subsequent annual vaccination seasons to evaluate changes associated with repeated vaccination.

  4. Frequency of influenza specific T cells following vaccination

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

    Influenza specific T cell responses will be assessed by measuring the frequency of antigen responsive T cells following stimulation with influenza antigens. Antigen specific T cells will be characterized using activation induced and functional markers.

Other outcomes

  1. Molecular immune signatures associated with influenza vaccine responses

    Time frame: Through study completion, up to 3 years

    Transcriptomic, miRNA, and proteomic analyses will be performed at selected time points to identify molecular signatures associated with vaccine induced immune responses, vaccine formulation, aging, and repeated annual vaccination. Integrated multiomics analyses will be used to explore molecular pathways and potential biomarkers associated with vaccine responsiveness.

  2. Extracellular vesicle associated molecular signatures following influenza vaccination

    Time frame: Through study completion, up to 3 years

    Molecular profiles of extracellular vesicles, including exosomes, will be explored to identify biomarkers associated with vaccine induced immune responses, immune aging, and repeated annual vaccination.

Interested in participating?

Recruiting

Interested in participating?

Request Info

Sponsors and collaborators

Lead sponsor

Korea University Guro Hospital

Other

Collaborators

  • National Research Foundation of Korea

Registry information

Official study title

Immunogenicity of Different Influenza Vaccine Strategies in Older Adults in a Repeated Vaccination Setting

Important dates

Study start
2026
Primary completion
2028
Study completion
2028
First posted
Sep 24, 2026
Registry last updated
Sep 24, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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