XK and influenza: In this study, we assessed the levels of neutralizing antibodies, HA head binding antibodies, functional NA inhibition antibodies (NAI), NA binding antibodies to HPAI clade 2.3.4.4b A(H5N1) viruses, and antibodies to group 1 HA stalk using 1794 sera collected from 723 participants (aged 0.5–88 yrs) from multiple geographic regions in the US across recent influenza seasons (2021–2024).