Cost-effectiveness of the adjuvanted quadrivalent influenza vaccine for older adults in South Korea

Figures & data

Figure 1. Model diagram of the seasonal influenza transmission and vaccination.

For simplicity, subscript $\mathit{k}$, representing age groups for each compartment, is not shown ($\mathit{k}=1,2,\dots ,17$).

Table 1. Description of epidemiological parameters and baseline values.

Age (years)
	0–4	5–9	10–14	15–19	20–24	25–29	30–34	35–39	40–44	45–49	50–54	55–59	60–64	65–69	70–74	75+
Vaccine efficacy (%)
QIV^Citation23
	0.625	0.625	0.625	0.590	0.540	0.540	0.540	0.540	0.540	0.540	0.540	0.540	0.540	0.478	0.478	0.453
aQIV^Citation17
														0.561	0.561	0.561
Proportion of requiring outpatient visits given symptomatic infection ^Citation21
	0.154	0.169	0.169	0.169	0.170	0.170	0.170	0.170	0.170	0.170	0.163	0.163	0.156	0.156	0.128	0.128
Proportion of hospitalization given symptomatic infection ^Citation21
	0.029	0.013	0.013	0.013	0.011	0.011	0.011	0.011	0.011	0.011	0.018	0.018	0.024	0.024	0.048	0.048
Probability of manifesting symptoms ^Citation24
0.670
Reporting delay ($\mathit{day})$^Citation25
1
Relative infectiousness of outpatients
0.5
Duration of latent period ($\mathit{day})$^Citation26
1.2
Recovery rate of outpatients $\left(\mathit{da}{y}^{-1}\right)$^Citation26
0.333
Recovery rate of symptomatically infected individuals who do not seek medical care $\left(\mathit{da}{y}^{-1}\right)$^Citation25
0.250
Recovery rate of infected individuals without symptoms $\left(\mathit{da}{y}^{-1}\right)$^Citation26
0.250
Recovery rate of hospitalization $\left(\mathit{da}{y}^{-1}\right)$^Citation27
	0.193	0.215	0.215	0.215	0.218	0.218	0.218	0.218	0.218	0.218	0.206	0.206	0.206	0.180	0.180	0.180
Death rate among inpatients ($\mathit{da}{y}^{-1},1\times {10}^{-2})$^Citation27
	0.002	0.004	0.004	0.004	0.020	0.020	0.020	0.020	0.020	0.020	0.100	0.100	0.100	0.560	0.560	0.560
Probability that an infectious contact leads to infection
	0.241	0.034	0.034	0.034	0.013	0.013	0.013	0.013	0.013	0.013	0.009	0.009	0.009	0.009	0017	0.017

Abbreviations: aQIV, adjuvanted quadrivalent influenza vaccine; QIV, quadrivalent influenza vaccine.

Table 2. Input data for cost, utilities, and disutilities used in the cost-effectiveness analysis.

Utilities and disutilities
Baseline for the healthy population^Citation31
1.00	1.00	1.00	1.00	0.97	0.97	0.97	0.97	0.97	0.97	0.96	0.96	0.94	0.89		0.89	0.89
Symptomatic influenza^Citation32–34
_–0.19 for 4 days
Hospitalization due to influenza^Citation32,Citation35,Citation36
_–0.41 for 5 days													_–0.41 for 6 days
QALY losses associated with deaths ^Citation37,Citation38
21.38	21.18	20.92	20.59	20.18	19.82	18.38	18.84	18.16	17.32	16.30	15.14	12.75	12.15		10.57	8.15
Cost (USD, $) ^Citation31
QIV per dose
8.10
aQIV per dose
-														14.58
Vaccine administration
15.08
Outpatient visit^Citation31
80.8	76.0	71.2	66.8	59.7	59.7	59.7	59.7	59.7	59.7	61.5	61.5	63.5	66.1		66.1	66.1
Hospitalization^Citation31
564.9	571.7	578.1	611.0	681.4	676.7	676.7	676.7	676.7	676.7	886.5	886.5	1,067.2	1,095.2		1,040.4	1,040.4

Abbreviations: aQIV, adjuvanted quadrivalent influenza vaccine; QALY, quality-adjusted life years; QIV, quadrivalent influenza vaccine.

Table 3. Health outcomes and overall costs (USD, $) for each seasonal influenza vaccination strategy.

	Vaccination Strategy*
	All receive QIV	Older adults receive aQIV
		Vaccine efficacy of aQIV
		56.1%	60.0%	65.0%
Number of cases
Symptomatic infections for all ages (65+ years)	2,678,487 (16,493)	2,662,811 (14,780)	2,656,193 (14,067)	2,647,740 (13,158)
Outpatient visits for all ages (65+ years)	1,109,579 (5,574)	1,104,021 (4,999)	1,101,658 (4,759)	1,098,640 (4,453)
Hospitalizations for all ages (65+ years)	158,766 (2,195)	156,948 (1,965)	156,196 (1,870)	155,236 (1,749)
Deaths for all ages (65+ years)	589 (139)	540 (125)	521 (119)	495 (111)
Costs ($, million, discounted)
Vaccination program	510.3	545.5	545.5	545.5
Treatment-disease	1,073.0	1,059.6	1,054.0	1,047.0
Total	1,583.2	1,605.1	1,599.5	1,592.5
QALYs (discounted)	28,547,078	28,547,828	28,548,145	28,548,549

*The analysis assumes that the overall vaccination coverage level is 40%.

Abbreviations: aQIV, adjuvanted quadrivalent influenza vaccine; QALY, quality-adjusted life years; QIV, quadrivalent influenza vaccine.

Table 4. Effects of vaccinating all individuals with QIV versus aQIV administration for adults ≥65 years on incremental costs (USD, $), incremental QALYs, and ICERs ($/QALY).

aQIV’s efficacy	Changes in costs ($)	Changes in QALYs	ICERs ($/QALY)
56.1%	21,945,868	750	29,267
60.0%	16,409,006	1,066	15,390
65.0%	9,329,831	1,471	6,344

Abbreviations: aQIV, adjuvanted quadrivalent influenza vaccine; ICER, incremental cost-effectiveness ratio; QALY, quality-adjusted life year; QIV, quadrivalent influenza vaccine.

Figure 2. Cost-effectiveness acceptability curves depicting the cost-effective probability of aQIV versus QIV based on the efficacy of aQIV.

The acceptability of cost-effectiveness was assessed for aQIV at three efficacy levels: 56.1% (represented by a yellow line), 60.0% (represented by a green line), and 65.0% (represented by a red line). The willingness-to-pay threshold is set at $34,998, shown as a dashed line.

aQIV, adjuvanted quadrivalent influenza vaccine; QIV, quadrivalent influenza vaccine.

Figure 3. One-way deterministic sensitivity analysis.

The vertical line indicates the incremental cost-effectiveness ratio of the baseline analysis, $29,267 per quality-adjusted life year.

Figure 4. Incremental cost-effectiveness ratios based on the total vaccination costs.

Incremental cost-effectiveness ratios for aQIV were assessed at three different efficacy levels: 56.1% (represented by a yellow line), 60.0% (represented by a green line), and 65.0% (represented by a red line). The horizontal line denotes the zero value. The threshold for willingness-to-pay is established at $34,998 (indicated by a dashed line), while the assumed cost of aQIV is set at $29.66 (marked by a vertical dotted line).

aQIV, adjuvanted quadrivalent influenza vaccine.

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