Cost-effectiveness of the adjuvanted quadrivalent influenza vaccine in the elderly Belgian population

Figures & data

Figure 1. Cost-effectiveness model.

Table 1. Epidemiological, clinical and utilities inputs.

	65–74 years	75 +years	Source
Population (in 2023)	1,239,022	1,124,603	[40]
Epidemiological data
Influenza attack rate among unvaccinated elderly adults	5%	5%	[29]
Influenza incidence rate among patients vaccinated with the standard-dose quadrivalent vaccine (estimation)	3%	3%	[29,31,41], Sciensano data
Vaccination coverage	53.2%	70.8%	[34]
Patients seeking ambulatory professional care	40.6%	75.4%	[3,35,37]
Probabilities of developing influenza-related complications (% hospitalization rate; % mortality rate)
Bronchitis	3.85% (1.0%; 0.03%)	3.85% (1.0%; 0.03%)	[4,20]
Pneumonia	1.46% (59.0%; 5.23%	1.46% (61.0%; 8.71%)	[4,20,38]
URTI	6.05% (1.0%; 0.03%)	6.05% (1.0%; 0.03%)	[4,20]
Myocarditis	0.89% (100%; 7.10%)	0.89% (100%; 7.10%)	[4,20,39], expert advice
Renal complications	0.18% (100%; 13.8%)	0.18% (100%; 29.83%)	[4,20], expert advice
CNS complications	0.35% (100%; 2.9%)	0.35% (100%; 2.9%)	[4,20], expert advice
COPD exacerbations	0.99% (59.0%; 0.03%)	1.42% (61%; 0.03%)	Derived from [3], expert advice
Myocardial infarction	0.13% (100%; 11.9%)	0.13% (100%; 22.33%)	[42], expert advice, adapted from [20]
Stroke	0.75% (100%; 28.20%)	1.79% (100%; 28.20%)	[43], expert advice, adapted from [20]
Vaccine effectiveness
aQIV (adjuvanted)	56.1%		[33,41], Sciensano
HD-QIV (high dose)	54.7%		[32,41], Sciensano
SD-QIV (standard dose)	40.2%		[31,41], Sciensano
Utilities and disutilities
Baseline	0.82	0.69	[44]
Symptomatic influenza	−0.15 for 5 weeks		[35]
Hospitalization due to complications other than MI or stroke	−0.38 for 9 to 12 days		[20]
Hospitalization due to MI/stroke	−0.2102 (MI)/-0.2554 (stroke)		[20,45]
Ambulatory care for complications	−0.13 for URTI −0.25 for bronchitis/pneumonia/COPD		[20] assumption

URTI, upper respiratory tract infection; MI; myocardial infarction; COPD, chronic obstructive pulmonary disease; CNS, central nervous system; aQIV, adjuvant quadrivalent influenza vaccine; HD-QIV: high dose quadrivalent influenza vaccine; SD-QIV: standard dose quadrivalent influenza vaccine.

Table 2. Economic burden inputs.

Resource use	NIHDI reimbursed *Unit cost (EUR)	Patient** cost (EUR)	Source
Vaccines
aQIV	€24.73	€8.71	Seqirus
SD-QIV	€12.94	€4.08	[15]
HD-QIV	€32.62	€11.14	[15]
Vaccine administration	€24	€6	[48]
Ambulatory professional care	€52.71	€27.74	[35,46]
Complications: hospitalization costs (mean)
Bronchitis/URTI	€14,055	€198.63	[4,45,49]
Pneumonia	€14,786	€198.63	[4,45,49]
Myocarditis/Myocardial infarction	€9,338	€198.63	[4,45,49]
Renal complications	€6,402	€198.63	[45,49,50]
CNS complications	€5,666	€198.63	[45,49,50]
COPD exacerbations	€12,729	€198.63	[4,45,49]
Stroke	€12,538	€198.63	[4,45,49]
Complications: ambulatory costs (mean)
Bronchitis/URTI	€52.44	€35.10	[35,46] assumptions
Pneumonia/COPD exacerbations	€1,060.33	€452.09	[38,46,50] assumptions

NIHDI, National Institute for Health and Disability Insurance.

*Public price reduced by the patient’s co-payment or cost reported at charge of NIHDI.

**Co-payment at charge of ordinary beneficiaries.

Table 3. Outcomes in number of events, LYs, QALYs, and costs during the influenza season.

Results in Belgian population aged 65+ years	Considering 62% vaccine coverage with aQIV	Considering 62% vaccine coverage with SD-QIV	Incremental
Outcomes in number of events, LYs and QALYs
Estimated number of infected patients seeking medical care	43,183	50,102	−6,920
Estimated number of infected patients being hospitalized	3,419	3,949	−530
Estimated number of patients who will die from influenza	410	477	−66
LYs	27,617,751	27,617,095	656
QALYs	18,927,513	18,927,062	451
Health care costs and savings
Cost for vaccination (vaccine + administration)	€70,920,601	€53,761,687	€17,158,914
Cost for ambulatory care	€3,544,711	€4,101,589	-€556,878
Cost of hospitalizations	€39,387,613	€45,511,298	-€6,123,684
Total health care costs	€113,852,925	€103,374,574	€10,478,351

aQIV, adjuvanted quadrivalent influenza vaccine; LYs, life years; QALYs, quality-adjusted life years; SD-QIV, standard quadrivalent influenza vaccine.

Table 4. ICER and effectiveness expressed in LYs and QALYs.

Outcomes	aQIV compared to SD-QIV
Incremental LYs	656
Incremental QALYs	451
Incremental health care costs	€10,478,351
ICER (in LYs)	€ 15967
ICER (in QALYs)	€ 15227

aQIV, adjuvanted quadrivalent influenza vaccine; ICER, incremental cost-effectiveness ratio; LYs, life years; QALYs, quality-adjusted life years; SD-QIV, standard quadrivalent influenza vaccine.

Figure 2. Deterministic sensitivity analysis (DSA) of the top 10 drivers apart from vaccine cost.

Figure 3. Cost-effectiveness plane.

Figure 4. Cost-effectiveness acceptability curve.

Table 5. Scenario analyses.

Parameters	Base case inputs	Scenario analysis inputs	ICER (base case: €15,227)
Comparator	SD-QIV	HD-QIV	Dominant
Influenza attack	5%	7.2% [23,30]	€7,608
Corresponding number of hospitalizations in SD-QIV strategy	3,949	5,686
Corresponding number of deaths in SD-QIV strategy	477	686
Price of adjuvanted influenza vaccine (NIHDI)	€24.73	€22.11	€9,686
Complications: cardiac decompensation due to worsening of heart failure	Not included	Included (frequency equal to that of myocarditis, based on expert opinion [16])	€11,904
Complications: mortality rate in nursing home (outpatient)	Not included	Included [20,38]	€14,617
Disutility and duration due to symptomatic influenza	−0.15 for 35 days [35]	−0.32 for 9 days [20]	€17,160
Discount rate on long-term effects	1.5%	0% 5%	€14,239 €17,314
Effectiveness of aQIV (vs. comparator SD-QIV)	3.2% relative superiority vs. HD-QIV	equal to HD-QIV	€17,721
Cost perspective	National payer (NIHDI); direct health care costs	National payer + patient perspective	€24,447

aQIV, adjuvanted quadrivalent influenza vaccine; HD-QIV, high dose quadrivalent influenza vaccine; NIHDI, National Institute for Health and Disability Insurance; SD-QIV, standard dose quadrivalent influenza vaccine.

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Data availability statement

All data used (except price of aQIV) in this analysis are publicly available from the sources cited in Table 1.