Public preferences and willingness to accept a hypothetical vaccine to prevent a pandemic in Japan: a conjoint analysis

Figures & data

Table 1. The hypothetical vaccine’s characteristics and situation in the questionnaire

Contextual factors	Variables
Effectiveness	100%	50%
Safety (prevalence rate of the severe side-effect)	0.10%	1%
Immunity duration	one year	life-time
Price (out of pocket)	JPY 2,500	JPY 5,000	JPY 10,000	JPY 20,000
Infected individuals/deaths	100,000/5,000	1,000,000/50,000	10,000,000/500,000

Table 2. Demographics of respondents

		Number of Individuals	Weighted (%)	Japan Population (%)
Number		2155
Gender
	Male	1069	49.6	48.6
	Female	1086	50.4	51.4
Age
	20–29	420	19.5	10.1
	30–39	429	19.9	11.0
	40–49	429	19.9	14.2
	50–59	436	20.2	13.5
	60–69	441	20.5	12.2
Occupation ^1
	Full-time worker (regular employment)	852	39.5	35.7
	Part-time/non-regular employment worker	532	24.7	18.6
	Self-employed	150	7.0	6.1
	Household worker/unemployed/student	621	28.9	39.6
Household income (JPY)^2
	< 2 million	252	11.7	19
	2 to 6 million	1099	51.0	45.6
	6 to 10 million	560	26.0	23.2
	10 million or more	244	11.3	12.1
Routine visit to healthcare facility (more than monthly)
	Yes	520	24.1
	No	1,635	75.9
Impact on household income due to COVID-19
	Higher income in 2020 than in 2019	137	6.4
	Identical	1157	53.7
	Lower income in 2020 than in 2019	861	40.0
Fear of unknown infectious disease
	Very scary	1065	49.4
	Fairly scared but currently not so scared	724	33.6
	Not scared	268	12.4
	Not scared at all	98	4.5

¹The demographics regarding occupation were included for those aged over 15 years [20].

²The income levels were classified for every million JPY and the income data were merged based on the annual average income of Japan, which was 5.5 million JPY.

Figure 1. Relationship between willingness to vaccinate and cost considering different vaccine variables. a. Willingness to receive a vaccine with 100% efficacy, lifetime immunity duration, and low toxicity b. Willingness to receive a vaccine with 100% efficacy, one-year immunity duration, and low toxicity c. Willingness to receive a vaccine with 100% efficacy, lifetime immunity duration, and high toxicity d. Willingness to receive a vaccine with 50% efficacy, lifetime immunity duration, and low toxicity

Figure 2. Relationship between willingness to vaccinate and cost considering fear level regarding COVID-19. a. Willingness to receive a vaccine with 100% efficacy, lifetime immunity duration, and low toxicity b. Willingness to receive a vaccine with 100% efficacy, one-year immunity duration, and low toxicity c. Willingness to receive a vaccine with 100% efficacy, lifetime immunity duration, and high toxicity d. Willingness to receive a vaccine with 50% efficacy, lifetime immunity duration, and low toxicity

Table 3. Individual factors associated with willingness to get the hypothetical vaccine

		Model 1				Model 2
	Coefficient	Standard error	OR (95% CI)	p_value	Coefficient	Standard error	OR (95% CI)	p_value
Price (> JPY 1,000)	−0.075	0.002	0.99992 (0.99992–0.99993)	0.000	−0.075	0.002	0.99992 (0.99992–0.99993)	0.000
Efficacy (100% vs. 50%)	1.581	0.026	4.858 (4.617–5.111)	0.000	1.580	0.026	4.855 (4.615–5.109)	0.000
Toxicity (1% vs. 0.1%)	−0.969	0.024	0.379 (0.362–0.398)	0.000	−0.969	0.024	0.379 (0.362–0.398)	0.000
Immunity duration (lifetime vs. 1 year)	0.972	0.024	2.642 (2.519–2.771)	0.000	0.971	0.024	2.642 (2.518–2.770)	0.000
Income (> JPY 1 million)					0.052	0.010	1.053 (1.032–1.074)	0.000
Fear of pandemic (extreme)					0.262	0.085	1.299 (1.100–1.534)	0.002
Fear of pandemic (moderate or more)					0.499	0.128	1.648 (1.281–2.119)	0.000
Fear of pandemic (low or more)					1.950	0.241	7.026 (4.285–11.259)	0.000
Constant	−1.741	0.050		0.000	−4.450	0.228		0.000
Log likelihood	−24,494.900				−24,393.597

OR: Odd ratios; CI: Confidence Intervals.

Kelly BJ, Southwell BG, and McCormack LA, et al. Predictors of willingness to get a COVID-19 vaccine in the U.S. BMC Infect Dis. 2021;21(1):338.

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