Currently, influenza subunit vaccines focus on haemagglutinin and contain minimal amounts of NA, despite emerging evidence from multiple studies indicating NA’s importance as an independent protective antigen (Kilbourne et al., 1995; reviewed in Air, 2012; Eichelberger et al., 2018; Giurgea et al., 2020; Rajendran et al., 2021; Zhang and Ross, 2024). Here, XK is linked to influenza.