Attack rate with coverage for scenarios A-D.

<p>Predicted attack rates for four different pandemic and vaccine action scenarios as a function of general population coverage with a CTL-inducing vaccine. In each panel the solid line corresponds to assumptions of relative infectiousness in vaccinated and unvaccinated naïve hosts of <i>ϵ</i>_v = 0.25, with dashed and dotted lines corresponding to <i>ϵ</i>_v = 0.5 and 0.75 respectively. Scenario A captures a population without pre-existing CTL-mediated immunity to the pandemic strain. In scenarios B and C, 80 per cent of the population have pre-existing CTL-mediated immunity (<i>f</i>_<i>E</i> = 0.8) suppressing infectiousness by 50 per cent (<i>ϵ</i> = 0.5), with vaccine action saturating (B) or boosting (C). Scenario D is a modification of scenario C that assumes 50 per cent of those with naturally acquired CTL immunity also have cross-reactive protective antibody.