Pandemic Inﬂuenza Mitigation Strategies Figure 2. Sensitivity analyses of clinical outcomes as key parameters are varied. In A–C, the clinical attack rate (CAR) is displayed as a function of R0 and vaccine efﬁcacy (VE) (A), vaccine coverage and VE (B), and the delay to vaccination (C). In D, deaths prevented per 100,000 population compared with no intervention is displayed as a function of R0. Economic Outcomes The total discounted healthcare costs for a pandemic in the absence of any intervention was $31.1/person in the population. The gross discounted cost over 5 years (includ- ing purchase, replacement, storage, and administration) of a prepandemic vaccination program was $68.4/person in the population and the cost of an antiviral treatment pro- gram (purchase, replacement, and storage only) over the same period was $24.8/person. The base-case results for the healthcare system per- spective are shown in Table 2. In the base-case model (R0 = 1.7, VE = 40%), strategies 2–4 each offered increased effectiveness at an increased cost when compared with the next best strategy. Under these conditions (theoretically), decision makers should ﬁrst decide if strategy 2 offers val- ue for money (incremental cost-effectiveness ratio [ICER] = $909/LYS) and then consider the value offered by each additional increase in spending, moving from strategy 2 to 3 (ICER = $1,084/LYS) and then from strategy 3 to 4 (ICER = $7,458/LYS). From a societal perspective the least costly strategy was prepandemic vaccination (strategy 3), which was cost saving when compared with the minimum pharmaceuti- cal intervention. Strategy 3 also dominated antiviral drug treatment alone (strategy 2), being more effective and less costly. The addition of antiviral drug treatment to prepan- demic vaccination cost $7,404/LYS. Sensitivity Analyses (Healthcare System Perspective) Key parameters affecting the cost-effectiveness of strat- egies included the R0 value and factors impacting vaccine or antiviral effectiveness. Because strategies differed in their sensitivity to these parameters, the cost-effectiveness of strategies relative to each other varied. Dominance occurs when a strategy is considered superior to the alternative by being either more effective and less costly (simple domi- nance) or more effective and more costly but with a lower ICER (extended dominance) (36). At higher values of VE (>41%) or when the percentage of antiviral given within 48 h was <75% (base-case = 80%), prepandemic vaccination dominated antiviral drug treatment alone. When the VE was >50% or the R <1.6, prepandemic vaccination alone 0 was largely sufﬁcient to contain the pandemic, and the ad- dition of antiviral treatment offered only a minimal incre- mental effect at a high incremental cost (ICER >$1million Table 2. Base-case economic results per person in the population (healthcare system perspective) of 4 pharmaceutical-based pandemic influenza mitigation strategies* Strategy no. Net cost Incremental cost LYS Incremental LYS Incremental cost per LYS† 1 65.88 – – – – 2 82.24 16.36 0.01803 0.01803 908 3 100.65 18.40 0.03501 0.01698 1,084 4 124.00 23.36 0.03814 0.00313 7,458 *LYS, life-year saved. Costs and life-years discounted at 5% annually; all costs calculated in 2005 Australian dollars. †Rounded to the nearest whole dollar. Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 16, No. 2, February 2010 227