Table 2.
Ten-year average annual scenario analyses results (2012–2022)a.
| Scenario settings | Cases avoided (IIV4 versus IIV3) | ICER (2013/2014 $ per QALY gained)b |
|---|---|---|
| Base case | 1,973,849 | −62,472 |
| Higher infectivityc (β = 0.000529, R0 = 3.5) | 3,593,862 | −50,598 |
| Lower infectivityc (β = 0.000256, R0 = 1.69) | 563,795 | +19,678 |
| Increased duration of natural immunity to type A influenza (Upper 95% CL [2.52 years]) | 1,973,849 | −62,469 |
| Decreased duration of natural immunity to type A influenza (Lower 95% CL [2.38 years]) | 1,973,849 | −62,484 |
| Increased duration of natural immunity to type B influenza (Upper 95% CL [15.44 years]) | 1,834,046 | −60,710 |
| Decreased duration of natural immunity to type B influenza (Lower 95% CL [13.94 years]) | 2,130,249 | −64,058 |
| Increased natural cross-protection (Upper 95% CL [Type A = 52.2%, Type B = 52.0%]) | 1,938,301 | −61,964 |
| Decreased natural cross-protection (Lower 95% CL [Type A = 44.3%, Type B = 48.3%]) | 2,012,049 | −62,993 |
| Increased amplitude of season variation factor (Upper 95% CL [0.472]) | 2,103,013 | −64,232 |
| Decreased amplitude of season variation factor (Lower 95% CL [0.443]) | 1,857,467 | −60,605 |
| Increased probability of selecting the correct B lineage (Upper 95% CL [71.2%]) | 1,925,708 | −62,269 |
| Decreased probability of selecting the correct B lineage (Lower 95% CL [65.3%]) | 1,973,849 | −62,472 |
| Fixed vaccine coverage projectionsd (at 2012 levels) | 2,489,427 | −70,708 |
| Increased percentage of children receiving 2 doses of IIV3 or IIV4e | 1,973,849 | −62,368 |
| Increased inpatient costs per case (base case +50%) | 1,973,849 | −74,198 |
| Decreased inpatient costs per case (base case −50%) | 1,973,849 | −50,745 |
| Lower vaccine administration cost (nurse setting; $20.06 visit + $25.08 administration) | 1,973,849 | −62,472 |
CL, confidence limit; ICER, incremental cost-effectiveness ratio; IIV3, trivalent inactivated influenza vaccine; IIV4, quadrivalent inactivated influenza vaccine; QALY, quality-adjusted life year.
All health and cost outcomes were discounted to 2012 using an annual discount rate of 3%.54
ICER includes direct medical costs, the cost for time lost for vaccination, and the cost for caregiver time lost for cases of influenza. Negative ICERs shown here indicate that vaccination with IIV4 yielded lower total costs and more QALYs than vaccination with IIV3.
Infectivity was varied from the base-case value of β = 0.000287 (R0 = 1.9).22
Vaccination coverage values for 2012–2022 were assumed to remain fixed at 2012–2013 values14 rather than following a projected increase over time.
Using age-specific estimates of percentages of children <9 years old who received 2 doses of vaccine.11