Background Influenza is a major global public health issue, particularly affecting older adults aged 65 years and above. Vaccination is the most effective strategy for preventing the spread of seasonal influenza and is recommended by the World Health Organization for high-risk groups. However, the prioritization and timing of vaccination across different risk groups are crucial factors affecting the success of vaccination programs.

Method In this study, we employed an age-structured SEIAHR model using seasonal influenza data from the Health Insurance Review and Assessment Service, and the influenza vaccination program in South Korea, as part of the Korean National Immunization Program. The transmission coefficients for various age groups and seasonality factors were estimated.

Results Our analysis reveals that under the baseline vaccination strategy, the highest infection rates occur in the G1 age group (children aged 0 to 14 years) and the early vaccination of the G4 group (individuals aged 65 years and older) is crucial for reducing severe outcomes. Specifically, scenarios prioritizing early vaccination for the elderly resulted in a reduction in cumulative cases by approximately 34% and a 45–60% decrease in peak infection levels compared with the baseline.

Conclusion These findings underscore that the targeted and timely vaccination of high-risk populations not only mitigates the overall epidemic burden but also shortens the period during which hospitalization thresholds are exceeded. Our study demonstrates that age-specific vaccination strategies, particularly those that accelerate vaccination in elderly individuals, are essential for minimizing the public health impact of seasonal influenza.

The authors have declared no competing interest.

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