Age-dependent immune landscapes affect influenza vaccine effectiveness and guide precision strategies.

Influenza vaccine effectiveness exhibits significant heterogeneity across age groups, largely shaped by lifelong immune remodeling. This review adopts a continuous spectrum perspective-spanning immune development, immune maturation, and immunosenescence-to delineate host immune responses to influenza across different life stages. Subsequently, the influence of these age-dependent differences on vaccine effectiveness is discussed. Based on these insights, an age-specific vaccine development strategy is proposed to guide differentiated vaccine optimization approaches for children, adults, and the elderly. This review provides a theoretical basis for transitioning from a "one-dose-fits-all" vaccination model and toward an age-specific precision paradigm.