Sensitivity of the cost effectiveness of school closure to the severity of influenza pandemic. Incremental cost effectiveness ratio (ICER), expressed as Japanese Yen per single life-year saved, is computed. Panel A examines ICER as a function of the reproduction number (ranging from 1.2 to 1.8) and the timing of school closure. Length of school closure in these panels is set at 7 days. It should be noted that the horizontal axis is at the ICER of 1.0 × 107 Yen/life-year. Panel B shows ICER as a function of the risk of death relative to assumed baseline of H1N1-2009 pandemic and the length of school closure. The relative risk of death of assumed pandemic is expressed as multiplier to the infection fatality risk of H1N1-2009 (e.g. if the relative risk is 50, the assumed pandemic is 50 times more likely lethal upon infection). The basic reproduction number and the timing of school closure in these panels are set at 1.4 and Day 60, respectively. Horizontal dashed grey line represents the threshold value of ICER, 1.0 × 107 Yen/life-year, below which one may regard the intervention as cost-effective.