Figure 6.
Illustration of the effect of potential vaccines targeting different influenza genes. (a) The fitness landscape in the absence of the immune response, re-plotted from figure 2. Two points with high fitness are marked (white triangle and circle). (b) The fitness landscape in the presence of a non-sterilizing antibody-based vaccine (modelled as w1 = 0.1). Overall fitness is reduced, the amount of reduction depending on the original location in the high-fitness region. In addition, a vaccine that targets HA will shift k+ to lower values, and a vaccine that mainly targets NA will shift k− to lower values. Possible HA or NA vaccines that reduce k+ or k− 10-fold are marked in the figure for two different initial locations of the virus. This can lead to additional loss of fitness, again depending on the location of the original strain on the fitness landscape. A vaccine that targets other genes, such as NP or M2, is not expected to shift stickiness. (Online version in colour.)