Cost-effectiveness analysis of quadrivalent influenza vaccination in at-risk adults and the elderly: an updated analysis in the UK

Figures & data

Table 1. UK population distributed by age group and risk status.

Age groups	Population distribution19	Distribution within age-group
		Healthy	At-risk
			Clinical at-risk12^,13^,22*	Residential care27†
18–49 years	43.99%	88.63%	11.38%	0.00%
50–64 years	18.23%	82.38%	17.63%	0.00%
65–69 years	4.86%	46.25%	48.75%	5.00%
70–74 years	3.88%	46.25%	48.75%	5.00%
75–79 years	3.19%	46.25%	48.75%	5.00%
80–84 years	2.38%	46.25%	48.75%	5.00%
>85 years	2.22%	46.25%	48.75%	5.00%

*Defined according to National Institute for Health and Care Excellence criteria15.

†Defined as people living in residential care facilities.

Table 2. Rate of movement from healthy status to at-risk status in each annual cycle by age*.

Age (years)	Rate	Age (years)	Rate	Age (years)	Rate	Age (years)	Rate
18	0.000,15
19	0.000,18
20	0.000,18
21	0.000,20	41	0.000,68	61	0.004,47	81	0.045,54
22	0.000,21	42	0.000,75	62	0.004,92	82	0.052,02
23	0.000,19	43	0.000,78	63	0.005,35	83	0.058,78
24	0.000,19	44	0.000,84	64	0.440,12	84	0.065,25
25	0.000,23	45	0.000,92	65	0.008,69	85	0.073,02
26	0.000,22	46	0.001,01	66	0.009,71	86	0.081,74
27	0.000,24	47	0.000,99	67	0.010,43	87	0.091,38
28	0.000,26	48	0.001,15	68	0.011,32	88	0.102,95
29	0.000,27	49	0.071,59	69	0.012,64	89	0.114,71
30	0.000,29	50	0.001,63	70	0.014,93	90	0.129,41
31	0.000,31	51	0.001,84	71	0.015,91	91	0.148,88
32	0.000,32	52	0.002,05	72	0.017,57	92	0.143,53
33	0.000,35	53	0.002,24	73	0.018,61	93	0.168,72
34	0.000,39	54	0.002,39	74	0.021,44	94	0.192,62
35	0.000,43	55	0.002,66	75	0.023,04	95	0.215,51
36	0.000,46	56	0.002,94	76	0.025,96	96	0.231,47
37	0.000,49	57	0.003,19	77	0.029,02	97	0.256,23
38	0.000,52	58	0.003,44	78	0.032,32	98	0.276,12
39	0.000,56	59	0.003,81	79	0.036,23	99	0.300,32
40	0.000,62	60	0.004,18	80	0.040,95	100	0.352,44

*Calculated from all-cause mortality data and the age distribution of the at-risk population19–21.

Table 3. Vaccine efficacy and coverage rates.

	Age group (years)
	18–49	50–64	65–69	70–74	75–79	80–84	85+
Vaccine efficacy against influenza A
Trivalent and quadrivalent vaccine	61.00%	61.00%	58.00%	58.00%	58.00%	58.00%	58.00%
Vaccine efficacy against influenza B
Trivalent vaccine*	63.69%	60.22%	57.28%	57.28%	54.28%	54.28%	54.28%
Quadrivalent vaccine†	77.00%	73.00%	69.00%	69.00%	66.00%	66.00%	66.00%
Vaccine coverage rates
Healthy	0%	0%	71.13%	71.13%	71.13%	71.13%	71.13%
At-risk	34.07%	100%	71.13%	71.13%	71.13%	71.13%	71.13%

*Allowing for cross-protection, and with vaccine matching to circulating strains of influenza B set at the average of the 10 seasons from 2002–2003 to 2012–2013, excluding the pandemic year of 2009–2010.

†Equivalent to the efficacy of the trivalent vaccine with optimal matching to circulating strains.

Table 4. Probabilities of events.

Parameter	Age group (years)
	18–49	50–64	65–69	70–74	75–79	80–84	85+
Probabilities related to infection and treatment
Receiving PEP*	2.10%	2.10%	1.36%	1.36%	1.36%	1.36%	1.36%
Resistance to PEP†	1.77%	1.77%	1.77%	1.77%	1.77%	1.77%	1.77%
Symptomatic influenza infection in absence of PEP, healthy,  and at-risk populations, identical for influenza A and B27	6.55%	6.55%	6.17%	6.17%	6.17%	6.17%	6.17%
Relative risk of symptomatic influenza after PEP compared  with no PEP26	22.62%	22.62%	22.47%	22.47%	22.47%	22.47%	22.47%
Seeking medical advice, healthy, and at-risk  populations10–13^,22^,29^,30	18.17%	19.22%	19.85%	19.85%	19.85%	19.85%	19.85%
Probability that medical advice is a GP visit (others are  A&E visits), healthy, and at-risk populations10^,11^,29^,30	99.73%	99.70%	99.30%	99.30%	99.30%	99.30%	99.30%
Probability of receiving neuraminidase inhibitors on seeking  medical advice, at-risk only26‡	16.00%	16.00%	11.00%	11.00%	11.00%	11.00%	11.00%
Probability of complication after GP or A&E visit without effective antiviral treatment$
Healthy10^,11^,29^,30	5.04%	5.31%	8.05%	8.05%	8.05%	8.05%	8.05%
At-risk10^,11^,29^,30	13.16%	11.88%	16.02%	16.02%	16.02%	16.02%	16.02%
Relative risk of complication after effective antiviral treatment,  at-risk only26	48.01%	47.64%	48.84%	48.84%	48.84%	48.84%	48.84%
Probability of hospitalization following any complication, %10–13^,22^,29^,30
Healthy	2.12%	4.31%	19.53%	19.53%	19.53%	19.53%	19.53%
At-risk	6.50%	16.06%	30.45%	30.45%	30.45%	30.45%	30.45%
Probability of death following hospitalization for any complication, %12^,13^,22
Healthy	1.14%	2.47%	18.16%	18.16%	18.16%	18.16%	18.16%
At-risk	2.89%	10.74%	26.77%	26.77%	26.77%	26.77%	26.77%
Probability of death following outpatient treatment for any complication, %10–13^,22^,29^,30
Healthy	0.08%	0.47%	12.85%	12.85%	12.85%	12.85%	12.85%
At-risk	0.23%	1.29%	8.46%	8.46%	8.46%	8.46%	8.46%

A&E, accident and emergency; GP, general practitioner; PEP, post-exposure prophylaxis.

*At-risk population only. Probabilities for clinical at-risk population without prior vaccination26; the same probabilities are assumed for the residential care population with or without vaccination as no distinction was made in the original source. The clinical at-risk population with previous vaccination did not receive post-exposure prophylaxis.

†Calculated as the mean of three reported values in adults28, elderly assumed to be the same as adults.

‡At-risk population only (neuraminidase treatment is not recommended for healthy individuals in the UK). Identical for GP and A&E visits. Probability of resistance to neuraminidase inhibitors 1.77% for all age groups, calculated as the mean of three reported values in adults28, elderly assumed to be the same as adults.

$Assumed that the probability is identical for patients not seeking medical advice.

Table 5. Age-dependent cost data.

Parameter	Age group (years)
	18–49	50–64	65–69	70–74	75–79	80–84	85+
Medication cost per script10^,11^,29^,30*	£0.07	£0.14	£1.04	£1.04	£1.04	£1.04	£1.04
Reimbursed home visits by nurse33-35*†	£0.014	£0.021	£0.356	£0.356	£0.356	£0.356	£0.356
Hospitalization for complications10^,11^,29^,30	£5,017.20	£7,597.89	£10,249.62	£10,249.62	£10,249.62	£10,249.62	£10,249.62
Outpatient treatment for complications10^,11^,29^,30	£74.66	£78.06	£78.73	£78.73	£78.73	£78.73	£78.73

*Weighted average accounting for differences between healthy and at-risk individuals and the distribution of the population between healthy and at-risk.

†Cost of home visits by nurse estimated from the probability of a home visit34, unit cost data for 201333, and assuming that adult patients would receive one visit and elderly patients would receive three35.

Table 6. Age-dependent cost data used only in the analysis from a societal perspective.

Parameter	Age group (years)
	18–49	50–64	65–69	70–74	75–79	80–84	85+
Prescription fees36–38
PEP	£1.67	£1.55	£0.00	£0.00	£0.00	£0.00	£0.00
Influenza without complications	£0.94	£0.88	£0.00	£0.00	£0.00	£0.00	£0.00
Influenza with complications, outpatient treatment	£1.46	£1.36	£0.00	£0.00	£0.00	£0.00	£0.00
Over-the-counter medication costs27^,34^,38^,39
Influenza without complications and without  medical advice	£1.97	£1.97	£1.49	£1.49	£1.49	£1.49	£1.49
Influenza without complications and with medical  advice	£0.91	£0.91	£0.91	£0.91	£0.91	£0.91	£0.91
Influenza with complications treated in outpatient  setting, or after hospital discharge	£0.91	£0.91	£0.91	£0.91	£0.91	£0.91	£0.91
Private nurse visits33–35
Influenza without complications	£0.007	£0.011	£0.063	£0.063	£0.063	£0.063	£0.063
Influenza with complications treated in outpatient  setting, or after hospital discharge	£0.007	£0.011	£0.189	£0.189	£0.189	£0.189	£0.189
Indirect costs
Time away from work and reduced productivity at work10^,11^,29^,30^,42^,43
No hospital treatment	£360.49	£360.49	£0.00	£0.00	£0.00	£0.00	£0.00
Hospitalization	£664.77	£1006.65	£0.00	£0.00	£0.00	£0.00	£0.00

PEP, post-exposure prophylaxis.

Table 7. Age-dependent costs of yearly productivity loss due to premature death*.

Age (years)	Cost	Age (years)	Cost	Age (years)	Cost	Age (years)	Cost
18	£479,120
19	£479,120
20	£479,120
21	£479,120	41	£282,267	61	£282,267	81	£24,107
22	£479,120	42	£282,267	62	£282,267	82	£24,107
23	£479,120	43	£282,267	63	£282,267	83	£24,107
24	£479,120	44	£282,267	64	£282,267	84	£24,107
25	£479,120	45	£282,267	65	£24,107	85	£24,107
26	£479,120	46	£282,267	66	£24,107	86	£24,107
27	£479,120	47	£282,267	67	£24,107	87	£24,107
28	£479,120	48	£282,267	68	£24,107	88	£24,107
29	£479,120	49	£282,267	69	£24,107	89	£24,107
30	£479,120	50	£282,267	70	£24,107	90	£24,107
31	£479,120	51	£282,267	71	£24,107	91	£24,107
32	£479,120	52	£282,267	72	£24,107	92	£24,107
33	£479,120	53	£282,267	73	£24,107	93	£24,107
34	£479,120	54	£282,267	74	£24,107	94	£24,107
35	£282,267	55	£282,267	75	£24,107	95	£24,107
36	£282,267	56	£282,267	76	£24,107	96	£24,107
37	£282,267	57	£282,267	77	£24,107	97	£24,107
38	£282,267	58	£282,267	78	£24,107	98	£24,107
39	£282,267	59	£282,267	79	£24,107	9	£24,107
40	£282,267	60	£282,267	80	£24,107	100	£24,107

*Productivity loss due to premature death is not included in the incremental cost-effectiveness ratio.

Table 8. Age-dependent utility data.

Parameter	Age group (years)
	18–49	50–64	65–69	70–74	75–79	80–84	85+
Baseline utility data45
Healthy	0.96	0.93	0.93	0.92	0.90	0.88	0.82
At-risk	0.91	0.82	0.80	0.78	0.75	0.70	0.65
Influenza not requiring hospitalization
Disutility46^,47	−0.68	−0.68	−0.88	−0.88	−0.88	−0.88	−0.88
Duration without effective neuraminidase inhibitor treatment47	7.5 days	7.5 days	7.5 days	7.5 days	7.5 days	7.5 days	7.5 days
Duration with effective neuraminidase inhibitor treatment47	5 days	5 days	5 days	5 days	5 days	5 days	5 days
Influenza requiring hospitalization
Disutility46^,47	−0.80	−0.80	−0.98	−0.98	−0.98	−0.98	−0.98
Duration10^,11^,29^,30	7.0 days	10.6 days	14.3 days	14.3 days	14.3 days	14.3 days	14.3 days

Table 9. Parameters used in the sensitivity analyses.

Parameter	PSA distribution	Range for one-way SA
Demographics
Percentage of population being clinically at-risk	Beta	95% CI
Percentage of population being residential	Beta	95% CI
Vaccine efficacy
TIV efficacy against influenza A in healthy and at-risk individuals	Lognormal	95% CI
QIV efficacy against influenza A in healthy and at-risk individuals		95% CI
TIV efficacy against influenza B with matching in healthy and at-risk individuals	Beta	Range
QIV efficacy against influenza B in case of mismatch in healthy and at-risk individuals	Beta	Range
Matching of B-strain in vaccine and circulation	Beta	Min–max
Circulation of B-strain	Beta	Min–max
Probabilities
Vaccination coverage rates in healthy and at-risk individuals	Beta	95% CI
Probability that ILI is influenza	Beta	95% CI
Proportion of clinically at-risk individuals without prior vaccination receiving PEP	Dependent on other parameters*	Min–max
Proportion of residential care individuals without prior vaccination receiving PEP	Dependent on other parameters*	Min–max
Proportion of residential care individuals with prior vaccination receiving PEP	Dependent on other parameters*	Min–max
Proportion of healthy and at-risk individuals resistant to PEP	Beta	95% CI
Probability of having influenza A in healthy and at-risk individuals (with no vaccination,  no PEP)	Lognormal	95% CI
Probability of having influenza B in healthy and at-risk individuals (with no vaccination,  no PEP)	Lognormal	95% CI
Relative risk of influenza following PEP in at-risk individuals	Lognormal	95% CI
Probability to seek for medical advice in healthy and at-risk individuals	Beta	95% CI
Probability to visit a GP in healthy and at-risk individuals	Beta	95% CI
Probability to receive NI after GP visit in at-risk individuals	Beta	95% CI
Probability to receive NI after A&E visit in at-risk individuals	Beta	95% CI
Probability to be resistant to NI in at-risk individuals	Beta	95% CI
Probability of complication after GP visit without effective NI treatment in healthy  and at-risk individuals	Beta	95% CI
Probability of complication after A&E visit without effective NI treatment in healthy  and at-risk individuals	Beta	95% CI
Relative risk to develop complications after NI treatment vs no NI treatment in  at-risk individuals	Lognormal	95% CI
Probability of complication without previous medical advice in healthy and  at-risk individuals	Beta	95% CI
Overall probability of a respiratory-related complication in healthy and  at-risk individuals	Beta	95% CI
Probability that a respiratory complication is pneumonia in healthy and  at-risk individuals	Beta	95% CI
Probability of cardiac complication in healthy and at-risk individuals	Beta	95% CI
Probability of renal complication in healthy and at-risk individuals	Beta	95% CI
Probability of CNS complication in healthy and at-risk individuals	Beta	95% CI
Probability of OM complication in healthy and at-risk individuals	Beta	95% CI
Probability of hospitalization having complication in healthy and at-risk individuals	Beta	95% CI
Probability of death after hospitalization for complication in healthy and  at-risk individuals	Beta	95% CI
Probability of death after outpatient treatment of complication in healthy and  at-risk individuals	Beta	95% CI
Reimbursable medical costs
Accident and Emergency visit cost	Gamma	95% CI
Cost per script	Gamma	95% CI
Cost of hospitalization with complication	Gamma	95% CI
Non-reimbursable costs (societal perspective)
Non-reimbursed OTC medication with uncomplicated influenza without medical advice  (no GP and no A&E visit)	Gamma	95% CI
Non-reimbursed OTC medication with uncomplicated influenza with medical advice  (GP and A&E visit)	Gamma	95% CI
Non-reimbursed OTC medication with outpatient treatment of complications	Gamma	95% CI
Non-reimbursed OTC medication related to a period after hospital discharge	Gamma	95% CI
Indirect costs
Absenteeism and presenteeism with uncomplicated influenza	Gamma	95% CI
Absenteeism and presenteeism because of hospitalization	Gamma	95% CI
Absenteeism and presenteeism because of treatment of an influenza complication  in an outpatient setting	Gamma	95% CI
Outcomes
Average utility of a healthy and at-risk individual	Normal	95% CI
Disutility with influenza (no NI treatment)	Gamma Lognormal	95% CI
Influenza duration (no NI treatment)	Gamma	95% CI
Disutility with influenza when NI treatment	Gamma Lognormal	Range
Influenza duration when NI treatment	Gamma	95% CI
Disutility with hospitalization of complication	Gamma Lognormal	Range
Duration of hospitalization with complication	Normal	95% CI
Disutility of outpatient treatment of complication	Gamma Lognormal	Range
Duration of outpatient treatment of complication	Normal	95% CI

*Dependent upon 8 other parameters: Probability influenza A at-risk; Probability influenza B at-risk; circulation influenza A; circulation influenza B; Probability NI treatment after GP visit; Probability of GP visit at-risk; Probability of NI treatment after A&E visit; Probability ILI is influenza.

A&E, accident and emergency; CI, confidence interval; CNS, central nervous system; GP, general practitioner; ILI, influenza-like illness; NI, neuraminidase inhibitor; OM, otitis media; OTC, over-the-counter; PEP, post-exposure prophylaxis; PSA, probabilistic sensitivity analysis; QIV, quadrivalent vaccine; SA, sensitivity analysis; TIV, trivalent vaccine.

Table 10. Base-case results from the NHS perspective in the base-case population over a lifetime.

	Trivalent vaccine	Quadrivalent vaccine	Quadrivalent compared with trivalent
Lifetime disease burden
Number vaccinated	741,827,739	741,974,804	−147,065
Number receiving PEP	3,597,241	3,597,902	−662
Number of influenza cases	120,853,828	119,440,436	1,413,392
Number seeking medical treatment for uncomplicated influenza	22,827,844	22,549,963	277,881
Number receiving antiviral treatment	590,664	568,776	21,888
Number with influenza complications	8,982,720	8,810,724	171,996
Number of hospitalizations for complications	1,245,156	1,203,375	41,780
Number of outpatient treatments for complications	7,737,564	7,607,349	130,216
Number of influenza deaths*	554,144	534,238	19,906
Health outcomes (discounted)
QALYs	956,326,785	956,378,323	51,538
Life-years	1,051,806,914	1,051,860,149	53,234
Costs (discounted)
Vaccination	£1,645,259,190	£2,543,745,127	£898,485,937
PEP	£84,612,381	£84,621,567	£9186
Treatment of uncomplicated influenza	£418,519,794	£414,666,370	−£3,853,424
Hospitalization for complications	£4,039,485,068	£3,903,387,067	−£136,098,001
Outpatient treatment of complications	£274,876,521	£271,257,173	−£3,619,347
Outpatient nurse costs	£4,675,848	£4,517,672	−£158,176
Total reimbursable medical costs	£6,467,428,803	£7,222,194,976	£754,766,174
Incremental cost-effectiveness ratio, quadrivalent vaccine vs trivalent vaccine (discounted)
£/QALY gained	–	–	£14,645
£/life-year gained	–	–	£14,178

NHS, National Health Service; PEP, post-exposure prophylaxis; QALY, quality-adjusted life-year.

*All deaths due to complications, as it was assumed that mortality from uncomplicated influenza was zero.

Table 11. Cost and ICER results from the societal perspective in the base-case population over a lifetime.

	Trivalent vaccine	Quadrivalent vaccine	Quadrivalent compared with trivalent
Costs (discounted)
Total reimbursable medical costs	£6,467,428,803	£7,222,194,976	£754,766,174
Non-reimbursable medical costs	£119,268,585	£118,402,781	−£865,804
Non-medical costs	£2,510,695,700	£2,509,598,167	−£1,097,533
Indirect costs, excluding costs of premature mortality	£18,764,166,876	£18,706,961,472	−£57,205,404
Total	£27,861,559,964	£28,557,157,397	£695,597,433
Premature mortality	£7,532,899,038	£7,292,117,439	−£240,781,599
Incremental cost-effectiveness ratio, quadrivalent vaccine vs trivalent vaccine (discounted)
£/QALY gained	–	–	£13,497
£/life-year gained	–	–	£13,067

ICER, incremental cost-effectiveness ratio; QALY, quality-adjusted life-year.

Table 12. Results from scenario analyses.

	Trivalent vaccine	Quadrivalent vaccine	Quadrivalent compared with trivalent
Scenario 1. Vaccination of elderly individuals (age 65+ years) only, NHS perspective, lifetime horizon (discounted)
Costs	£6,439,273,123	£6,988,232,025	£548,958,902
QALYs	956,223,307	956,269,060	45,753
ICER (£/QALY)	–	–	£11,998
Base-case for comparison (discounted)
Costs	£6,467,428,803	£7,222,194,976	£754,766,174
QALYs	956,326,785	956,378,323	51,538
ICER (£/QALY)	–	–	£14,645
Scenarios showing seasonal variation in matching between trivalent vaccine and circulating viruses, NHS perspective, vaccination of elderly and at-risk individuals, first-year results
Scenario 2. Worst-matching season
Costs	£285,613,027	£293,446,029	£7,833,002
QALYs	45,770,225	45,772,858	2,633
Scenario 3. Best-matching season
Costs	£260,228,182	£297,516,665	£37,288,483
QALYs	45,772,483	45,772,483	0
Base-case for comparison
Costs	£270,446,038	£301,929,691	£31,483,653
QALYs	45,771,559	45,772,078	519

ICER, incremental cost-effectiveness ratio; NHS, National Health Service; QALY, quality-adjusted life-year.

Table 13. Results from the NHS perspective in the base-case population over a 10-year time horizon.

	Trivalent vaccine	Quadrivalent vaccine	Quadrivalent compared with trivalent
10-year disease burden
Number vaccinated	93,709, 689	93,715,972	−6283
Number receiving PEP	667,908	667,935	−27
Number of influenza cases	27,757,780	27,573,936	183,844
Number seeking medical treatment for uncomplicated influenza	5,167,678	5,131,870	35,808
Number receiving antiviral treatment	100,656	97,257	3399
Number with influenza complications	1,809,611	1,787,187	22,425
Number of hospitalizations for complications	161,228	156,357	4871
Number of outpatient treatments for complications	1,648,384	1,630,830	17,554
Number of influenza deaths*	60,115	57,973	2142
Health outcomes (discounted)
QALYs	380,399,978	380,409,294	9316
Life-years	414,236,076	414,243,774	7698
Costs (discounted)
Vaccination	£523,231,926	£808,903,912	−£285,671,986
PEP	£31,311,522	£31,312,717	−£1195
Treatment of uncomplicated influenza	£168,778,955	£167,538,856	£1,240,098
Hospitalization for complications	£1,245,541,851	£1,204,740,306	£40,801,546
Outpatient treatment of complications	£108,284,010	£107,097,774	£1,186,236
Outpatient nurse costs	£1,445,731	£1,400,194	£45,537
Total reimbursable medical costs	£2,078,593,996	£2,320,993,759	−£242,399,763
Incremental cost-effectiveness ratio, quadrivalent vaccine versus trivalent vaccine (discounted)
£/QALY gained	–	–	£26,019
£/life-year gained	–	–	£31,489

NHS, National Health Service; PEP, post-exposure prophylaxis; QALY, quality-adjusted life-year.

*All deaths due to complications, as it was assumed that mortality from uncomplicated influenza was zero.

Figure 1. One-way sensitivity analysis comparing quadrivalent with trivalent vaccination. (A) Effect of the two most important parameters. (B) Effect of the next ten most important parameters. The vertical axis indicates the incremental cost-effectiveness ratio (ICER) in the base-case = £14,645/QALY. QALY, quality-adjusted life-year; TIV, trivalent vaccination; VE, vaccine efficacy.

Table 14. Effects of disutility and vaccine price in sensitivity analysis, base-case population over a lifetime.

	ICER (£/QALY gained)
	Low value	High value
Disutility for influenza with no NI treatment (low value −0.1, high value −1.6)
Age 18–49 years	£14,803	£14,400
Age 50–64 years	£14,949	£14,187
Age 65–69 years	£15,101	£14,586
Age 70–74 years	£15,074	£14,590
Age 75–79 years	£15,021	£14,596
Age 80–84 years	£14,938	£14,607
Age 85–100 years	£14,949	£14,606
Trivalent vaccine price (low value £5.22, high value £9.05)
Age 18–49 years	£15,144	£13,563
Age 50–64 years	£15,636	£12,498
Age 65–69 years	£15,745	£12,263
Age 70–74 years	£15,684	£12,395
Age 75–79 years	£15,559	£12,665
Age 80–84 years	£15,363	£13,089
Age 85–100 years	£15,389	£13,033

ICER, incremental cost-effectiveness ratio; QALY, quality-adjusted life-year; NI, neuraminidase inhibitor.

Table 15. Effects of discount rates in sensitivity analysis, base-case population over a lifetime.

	ICER (£/QALY gained)
Discount rate	NHS perspective	Societal perspective
0%	£11.539	£10,871
1.5%	£12,812	£11,941
5%	£16,017	£14,677

ICER, incremental cost-effectiveness ratio; NHS, National Health Service; QALY, quality-adjusted life-year.

Figure 2. Probabilistic sensitivity analysis comparing quadrivalent with trivalent vaccination, 1000 iterations. ICER, incremental cost-effectiveness ratio; QALY, quality-adjusted life-year; QIV, quadrivalent vaccination; TIV, trivalent vaccination.

Figure 3. Cost-effectiveness acceptability curve comparing quadrivalent with trivalent vaccination. QALY, quality-adjusted life-year; QIV, quadrivalent vaccination; TIV, trivalent vaccination.

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