Influenza Vaccine Immunogenicity in Repeatedly Vaccinated Older Adults

Phase 4RecruitingNCT07838298

Korea University Guro Hospital180 enrolled

Overview

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.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

NONE

Enrollment

180

Conditions

Influenza Vaccination Older Adults (65 Years and Older)

Interventions

Standard dose influenza vaccineBIOLOGICAL

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

MF59 adjuvanted influenza vaccineBIOLOGICAL

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

High dose influenza vaccineBIOLOGICAL

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

Eligibility

Sex: ALLMin age: 19 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

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.

Time frame: 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.

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

Secondary Outcomes

Seroconversion rate following influenza vaccination

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.

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

Frequency of influenza specific B cells following vaccination

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.

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

normalized level of influenza specific secretory IgA in nasal samples

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.

Time frame: 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

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.