XK and infection: Likewise, a passive transfer of sera from MVA-N3 vaccinated mice into naive mice demonstrated protection against H7N3 infection (Meseda et al., 2018) In contrast, mice that received sera from the MVA-N7 vaccine were not protected against challenge with H7N3 despite the vaccine containing an NA from the same subtype as N3, suggesting that further optimization of this vaccine approach is required to elicit broader NA-based protection (Meseda et al., 2018).