On both the HA and NA phylogenies, clade a contains the antigenically novel A/Brisbane/10/2007 isolate selected for the 2008–2009 vaccine, whereas only three 2006–2007 singleton isolates (i.e. isolates that were phylogenetically isolated; described below) belong to the clade that contains the 2006–2007 influenza vaccine strain A/Wisconsin/67/2005, confirming prior observations of a vaccine mismatch (Figure 6) [30]. The gene discussed is XK; the disease is influenza.