Lowering the recommended age for the free and active offer of influenza vaccination in Italy: clinical and economic impact analysis in the Liguria region

Figures & data

Figure 1. Flow diagram of study population in the model

Table 1. Input data

	Age group
	50–54			55–59			60–64
Input	WRF	NRF	Total	WRF	NRF	Total	WRF	NRF	Total
Target population (n, % [95% CI])	31,158 (23.5% [21.6–24.8])	101,484 (76.5% [75.2–78.4])	132,642 (100%)	34,385 (28.6% [26.8–30.1])	85,927 (71.4% [69.9–73.2])	120,312 (100%)	38,836 (37% [36–37.3%]	66,239 (63% [63–64.1])	105,075 (100%)
Seasonal Incidence of ILI/LRTI ED accesses (per 100 inhabitants), years 2011–2017 (median)	0.483	0.148		0.483	0.186		0.652	0.168
Probability (%) of ILI/LRTI requiring ED access	7.55	2.31		7.55	2.91		10.19	2.63
Probability (%) of ILI/LRTI requiring hospitalization among ED accesses (%)			44.4			49.7			62.6
QIV effectiveness Lineage A Lineage B			61% 73%
QIV (€)			5.78			5.78			5.78
Cost of administration (€)			6.16			6.16			6.16
ED Access (€)			296.25			296.25			296.25
ED Access followed by hospitalization (€)	2,158	1,416		2,577	1,600		3,134	1,977
GP consultation Probability of generating the cost for patients with influenza (%) Costs (€)			60 20.66			60 20.66			60 20.66
Antibiotic therapy Probability of generating the cost for patients with influenza (%) Costs (€)			47.3 3.06			47.3 3.06			47.3 3.06
Antiviral therapy Probability of generating the cost for patients with influenza (%) Costs (€)			0.17 38.5			0.17 38.5			0.17 38.5

Abbreviations. CI: Confidence Interval; WRF: With Risk Factors; NRF: No Risk Factors; ILI: Influenza-Like Illness; LRTI: Lower Respiratory Tract Infection; ED: Emergency department; QIV: Quadrivalent Influenza Vaccine; GP: General Practitioner.

Table 2. Base-case and hypothetical scenarios

Scenario	Age-range (years)	Condition	Vaccine coverage (%)	Subjects (n)
Base case	50–64	WRF	26.7%	27,869
		NRF	6.4%	16,233
Scenario 1	50–64	WRF	50%	52,189
		NRF	10%	25,365
Scenario 2	50–64	WRF	35%	36,532
		NRF	25%	63,413
Scenario 3	50–64	WRF	50%	52,189
		NRF	25%	63,413
Scenario 4	50–64	WRF	35%	36,532
		NRF	10%	25,365

Abbreviations. WRF: With Risk Factors; NRF: No Risk Factors.

Table 3. Base-case scenario: health outcomes and costs stratified by age-group and risk factor

Variables (n)	Age-group (years)	WRF	NRF	Total
Subjects	50–54	8,319	6,495	14,814
	55–59	9,181	5,499	14,680
	60–64	10,369	4,239	14,608
	Total	27,869	16,233	44,102
Overall cases	50–54	1,655	6,230	7,885
	55–59	1,826	5,274	7,100
	60–64	2,062	4,066	6,128
	Total	5,543	15,570	21,113
ED access	50–54	125	144	269
	55–59	138	153	291
	60–64	210	107	317
	Total	473	404	877
Cases with complications	50–54	886	1,637	2,523
	55–59	978	1,385	2,363
	60–64	1,105	1,068	2,173
	Total	2,969	4,090	7,059
Hospitalization	50–54	55	64	119
	55–59	68	76	145
	60–64	132	67	198
	Total	255	207	462
Vaccine costs (€)	50–54	48,084	37,541	85,625
	55–59	53,066	31,784	84,850
	60–64	59,933	24,501	84,434
	Total	161,083	93,827	254,910
Flu shot administration costs (€)	50–54	30,747	24,006	54,753
	55–59	33,933	20,324	54,257
	60–64	38,324	15,667	53,991
	Total	103,004	59,997	163,001
Clinical costs (€)	50–54	246,382	360,274	606,656
	55–59	316,320	359,501	675,821
	60–64	586,154	311,884	898,038
	Total	1,148,856	1,031,659	2,180,515
Total costs (€)	50–54	325,212	421,821	747,033
	55–59	403,319	411,610	814,929
	60–64	684,411	352,053	1,036,464
	Total	1,412,943	1,185,483	2,598,426

Abbreviations. WRF: With Risk Factors; NRF: No Risk Factors; ED: Emergency Department.

Figure 2. Epidemiological variations between the scenarios and the base case

Figure 3. Economic variations between the scenarios and the base case