Economic evaluation of varicella vaccination strategies in Jiangsu province, China: a decision-tree Markov model

Figures & data

Table 1. Description of different varicella vaccination strategies*

Strategy	Description
No vaccination	No varicella vaccination performed
Direct vaccination (1-dose)	1-dose vaccination for children
Direct vaccination (2-dose)	2-dose vaccination for children
Selective vaccination (1-dose)	1-dose varicella vaccination performed for children without protective antibody according to the serotesting before vaccination
Selective vaccination (2-dose)	2-dose varicella vaccination performed for children without protective antibody according to the serotesting before vaccination

*1-dose of varicella vaccination at 12 months, and 2-dose varicella vaccination at 15 months of age.

Figure 1. Decision-tree for varicella vaccination.

Table 2. Parameters of the varicella vaccine in the model

Parameters	Baseline value	Range	Distribution	Source
Epidemiologic variables
Case-fatality rate	0.000	0.000, 0.020	Beta (0,100)	10,26–28
Hospitalization rate	0.0152	0.000003, 0.049	Triangular (0.000003,0.0152,0.049)	Field work, 26,29–32
Natural immunity rate	0.171	±20%	Triangular (0.1368, 0.1710, 0.2052)	33
Varicella infection probability		-	-	Field work
0–4 years	0.0133	±20%	-
5–9 years	0.0232	±20%	-
10–14 years	0.0124	±20%	-
15–19 years	0.0033	±20%	-
20–24 years	0.0008	±20%	-
25–29 years	0.0021	±20%	-
30–34 years	0.0016	±20%	-
35–39 years	0.0007	±20%	-
≥40 years	0.0000	±20%	-
Asymptomatic rate	0.40	±20%	-	Assumption
Mortality rate	0.00703	-	-	25
Complications proportion among outpatients	0.000	0.000, 0.147	-	Field work, 36,37
Complications proportion among inpatients	0.000	0.000, 0.827	-	Field work, 36,37
Vaccination and Screen variables
Vaccine efficacy (1-dose)	0.81	0.78, 0.84	-	3
Vaccine waning rate (1-dose)	0.02	0.01, 0.05	-	39,40
Vaccination coverage (1-dose)	0.60	0.10, 1.00	-	9
Vaccine efficacy (2-dose)	0.92	0.88, 0.95	-	3
Vaccine waning rate (2-dose)	0.00	0.00, 0.01	-	39,40
Vaccination coverage (2-dose)	0.60	0.10, 1.00	-	9
Serologic test sensitivity	0.97	0.86, 0.97	-	41
Serologic test specificity	0.99	0.82, 0.99	-	41
Cost (USD)
Vaccine (per dose)	20.14	7.78, 40.43	Triangular (7.78, 20.14, 40.43)	Field work, 14–16,42
Administration (per dose)	2.96	1.19, 4.35	Triangular (1.19, 2.96, 4.35)	Field work, 14,16,42
Average medical cost per outpatient without complications	68.48	62.91, 203.23	Gamma (1, 68.48)	Field work, 14–16,32,44
Average medical cost per outpatient with complications	136.96	125.82, 406.46	-	Assumption
Average medical cost per inpatient without complications	581.41	348.17, 766.25	Gamma (1, 581.41)	Field work, 14–16,32
Average medical cost per inpatient with complications	1162.82	696.34, 1532.5	-	Assumption
Average medical cost per dead patient	10,000.00	8,000.00, 12,000.00	-	Assumption
Serologic test (per unit)	14.81	10.00, 25.00	Triangular (10.00, 20.00, 25.00)	Field work, 45,46
Utility weights (QALY loss)
Health	1	-	-	Assumption
Asymptomatic	0.0005	-	-	Assumption
Outpatient without complications	0.01	0.001, 0.02	Triangular (0.001, 0.01, 0.02)	47
Outpatient with complications	0.1	±50%	-	Assumption
Inpatients without complications	0.02	0.01, 0.10	Triangular (0.01, 0.02, 0.1)	47
Inpatients with complications	0.2	±50%	-	Assumption
Other Parameters
Per capita GDP(USD)	15,875.62	-	-	25
Discount rate	0.03	0.01, 0.05	-	48

Table 3. Cost-utility and cost-effectiveness outcomes for different varicella vaccination strategies

Variables	No vaccination	1-dose vaccination		2-dose vaccination
		Direct vaccination	Selective vaccination	Direct vaccination	Selective vaccination
Mean Cost (USD)	6.99	17.84	36.73	30.83	54.62
Mean QALYs	49.12337	49.12388	49.12407	49.12405	49.12430
No. of cases	11,588	3527	4931	887	2751
ICUR* (USD per QALY saved)	-	21,401.33	42,623.62	35,420.81	51,406.35
ICUR** (USD per QALY saved)	-	-	99,005.91	78,216.24	87,675.02

* compared with no vaccination, ** compared with 1-dose direct vaccination, QALY: quality adjusted life year, ICUR: incremental cost-utility ratio, ICER: incremental cost-effectiveness ratio.

Figure 2. Tornado diagram of parameters in models*.

*2a represented the tornado analysis of 1-dose vaccination (direct) versus no vaccination; 2b: tornado analysis of 2-dose vaccination (direct) versus no vaccination; 2 c: tornado analysis of 1-dose vaccination (selective) versus no vaccination; 2d: tornado analysis of 2-dose vaccination (selective) versus no vaccination. The line in the Figure 2 was willingness-to-pay threshold (3-time per-capital GDP). The five parameters most sensitive to the results were listed in the graph.

Figure 3. Cost-effectiveness acceptability curve*.

* This graph illustrates the results of a probabilistic sensitivity analysis, comparing five possible immunization strategies. GDP: Gross Domestic Product.

Data Availability Statement

Some or all data, models, or code generated or used during the study are available from the corresponding author by request.