Figure 4.  Effect of timing of epidemic peak on preferred vaccination strategy.  Total model-predicted attack rates and deaths by month of the pandemic peak are shown, when implementing attack rate (AR)-  or outcome-based vaccination strategies.  For each month of the epidemic peak, outcomes are presented for three values of pre-existing immunity among individuals aged ≥53 (30%, 50%, and 70%) and two vaccination coverage levels (base case and upper bound).  For all scenarios, vaccination campaigns are initiated on November 15, 2009.