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experiment, coronavirus, vaccine choice, vaccine hesitancy, psychology
Amidst the global struggle to achieve herd immunity against COVID-19, this study investigates whether the number of vaccine options (the size of the choice set) predicts the public’s intention to get vaccinated, and whether this effect depends on their trust in institutions – a system in which a collection of actors – from scientists and vaccine developers to public servants and front-line health workers – is working to fight the pandemic and to develop and approve vaccines against COVID-19 and deliver them to the public. Using an online experiment conducted in Japan (N = 600), the study tested whether choice set sizes of 1, 2, and 4 make a difference in the intention to get vaccinated. The study found that the intention was higher when the subjects were given two vaccine options to choose from, rather than offered a single vaccine, when trust was low, but this effect was negative when the subject trusted institutions highly. The study did not find strong evidence to support the effect of presenting a choice set of four. Based on these findings, this study offers nuanced suggestions for vaccine policy.