Next, we review how the new mutations affect vaccine development through altering antibody interactions as well as antigenic regions. There are 3 crystal structures of related neuraminidases in complex with antibodies [41] [42] [43] . In Figure 5 , we annotate residues that are within 3 Å distance to the respective bound antibody and, hence, crucial for the interaction. Interestingly, residues in sites recognized by both NC41 and NC10 antibodies appear mutated in the new strain. This would suggest that these old antibodies (that were originally directed against N9 neuraminidase) would probably not bind to NA of the new strain. Nevertheless, using the same regions as epitope may be a viable option for novel vaccine development.