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

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

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.

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

Inclusion Criteria:

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

Exclusion Criteria:

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