Acceptability of mandatory vaccination: a survey experiment on the effects of thresholds and justifications

Figures & data

Figure 1. The structure of the experiment.

A flowchart showing how the experiment progressed. First stage: scenario introduction. Second stage: Randon assignment to one of the two threshold level conditions (70% or 90%). Third stage: random assignment to one of the three justification conditions (economic stability, health-care or individual rights and freedoms). Final stage: questions measuring the dependent variables.

Table 1. Descriptive statistics.

	N	Min.	Max.	Mean	Std. Deviation
Acceptability of mandatory vaccination	1030	0.00	10.00	7.34	2.95
Willingness to take a non-mandatory vaccine	1008	0.00	10.00	8.98	2.18
Refusal to take a mandatory vaccine	940	0.00	10.00	0.84	2.06

Figure 2. The means of the dependent variables across experimental treatments. Note: The error bars show the boundaries of the 95% confidence interval. The labels refer to justifications, followed by thresholds for herd immunity in parentheses.

Bar chart of the levels of the three outcome variables on a scale from 0 to 10, clustered by treatment group. Acceptability of mandatory vaccination varies between 6.5 and 8, whereas willingness to take a non-mandatory vaccine varies between 8 and 9.5. Refusal to take a mandatory vaccine varies between 0.5 and 1.5. Acceptability of mandatory vaccination is lower and refusal to take the vaccine is higher in control group and the health/70% group, compared to other treatment groups.

Table 2. Two-way ANOVA results. Dependent variable: Acceptability of mandatory vaccination.

Source	F	df	p	Effect size
Corrected model	6.67	6	0.000	0.04
Justification	2.80	2	0.061	0.01
Threshold	1.90	1	0.168	0.00
Justification × Threshold	8.80	2	0.000	0.02
	SS		MS
Error	8131.60	945	8.61
Corrected total	8475.90	951

Note: Effect sizes are partial eta². SS denotes type III sum of squares and MS mean square. P values are two-tailed.

Figure 3. The estimated marginal means of the acceptability of mandatory vaccination. Note: The error bars show the boundaries of the 95% confidence interval.

The scale of estimated marginial means goes from 5.5 to 8.5 in the figure.

Table 3. Two-way ANOVA results. Dependent variables: Willingness to take a non-mandatory vaccine and Refusal to take a mandatory vaccine.

	Willingness to take a non-mandatory vaccine				Refusal to take a mandatory vaccine
Source	F	df	p	Effect size	F	df	p	Effect size
Corrected model	3.57	6	0.002	0.02	2.05	6	0.057	0.01
Justification	1.91	2	0.148	0.00	2.02	2	0.134	0.01
Threshold	7.64	1	0.006	0.01	2.50	1	0.114	0.00
Justification × Threshold	4.43	2	0.012	0.01	2.70	2	0.068	0.01
	SS		MS		SS		MS
Error	4528.32	923	4.91		3789.52	861	4.40
Corrected total	4633.26	929			3843.54	867

Note: Effect sizes are partial eta². SS denotes type III sum of squares and MS mean square. P values are two-tailed.

Figure 4. The estimated marginal means of the willingness to take a non-mandatory vaccine. Note: The error bars show the boundaries of the 95% confidence interval.

The scale of estimated marginal means ranges from 7.5 to 10 in the figure.