XK and influenza: Although influenza vaccine development has traditionally focused on HA, NA has emerged as an effective vaccine target in the past few years because recent studies have shown that NA immunity has a significant role in protection against influenza infection (Monto et al., 2015; Weiss et al., 2020; Couch et al., 2013; Memoli et al., 2016; Krammer et al., 2018).