Background Opinion polls on vaccination intentions suggest that COVID-19 vaccine hesitancy is increasing worldwide; however, the usefulness of opinion polls to prepare mass vaccination campaigns for specific new vaccines and to estimate acceptance in a country's population is limited. We therefore aimed to assess the effects of vaccine characteristics, information on herd immunity, and general practitioner (GP) recommendation on vaccine hesitancy in a representative working-age population in France. MethodsIn this survey experiment, adults aged 18-64 years residing in France, with no history of SARS-CoV-2 infection, were randomly selected from an online survey research panel in July, 2020, stratified by gender, age, education, household size, and region and area of residence to be representative of the French population. Participants completed an online questionnaire on their background and vaccination behaviour-related variables (including past vaccine compliance, risk factors for severe COVID-19, and COVID-19 perceptions and experience), and were then randomly assigned according to a full factorial design to one of three groups to receive differing information on herd immunity (>50% of adults aged 18-64 years must be immunised [either by vaccination or infection]; >50% of adults must be immunised [either by vaccination or infection]; or no information on herd immunity) and to one of two groups regarding GP recommendation of vaccination (GP recommends vaccination or expresses no opinion). Participants then completed a series of eight discrete choice tasks designed to assess vaccine acceptance or refusal based on hypothetical vaccine characteristics (efficacy [50%, 80%, 90%, or 100%], risk of serious side-effects [1 in 10 000 or 1 in 100 000], location of manufacture [EU, USA, or China], and place of administration [GP practice, local pharmacy, or mass vaccination centre]). Responses were analysed with a two-part model to disentangle outright vaccine refusal (irrespective of vaccine characteristics, defined as opting for no vaccination in all eight tasks) from vaccine hesitancy (acceptance depending on vaccine characteristics). Findings Survey responses were collected from 1942 working-age adults, of whom 560 (28•8%) opted for no vaccination in all eight tasks (outright vaccine refusal) and 1382 (71•2%) did not. In our model, outright vaccine refusal and vaccine hesitancy were both significantly associated with female gender, age (with an inverted U-shaped relationship), lower educational level, poor compliance with recommended vaccinations in the past, and no report of specified chronic conditions (ie, no hypertension [ for vaccine hesitancy] or no chronic conditions other than hypertension [ for outright vaccine refusal]). Outright vaccine refusal was also associated with a lower perceived severity of COVID-19, whereas vaccine hesitancy was lower when herd immunity benefits were communicated and in working versus nonworking individuals, and those with experience of COVID-19 (had symptoms or knew someone with CO...

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Eliciting sincere preferences for non-market goods remains a challenge due to hypothetical bias -the so-called gap between hypothetical monetary values and real economic commitments. The gap arises because people either overstate hypothetical values or understate real commitments or a combination of both. Herein we examine whether the traditional real-world institution of the solemn oath can improve preference elicitation. Applying the social psychology theory on the oath as a truth-telling-commitment device, we ask our bidders to swear on their honour to give honest answers prior to participating in an incentive-compatible second-price auction. Results from our induced valuation testbed treatments suggest the oath-only auctions outperform all other auctions (real, hypothetical, and real-with-oath). In our homegrown valuation treatments eliciting preferences for dolphin protection, the oath-only design induced people to treat as binding both their budget constraint (i.e ., lower values on the high end of the value distribution) and participation constraint (i.e., positive values rather than zero bids used to opt out of auction). Our oath-only results are robust to extra training on the auction and to consequential wording about the reason for the oath. RésuméLa révélation des préférences des individus à l'égard des biens non-marchands reste une question largement ouverte en raison de l'existence d'un problème de biais hypothètique -qui désigne la différence généralement observée entre les valeurs monétaires déclarées dans un contexte hypothètique et les engagements financiers effectifs des individus. Ce biais apparaît à la fois parce que les individus sur-estiment leur vraie valeur dans un contexte hypothètique et parce qu'ils sous-estiment leur véritable engagement financier dans un contexte réel. Cet article cherche à évaluer dans quelle mesure une procédure de serment solennel peut permettre d'améliorer les mécanismes de révélation des préférences au regard de ces deux dimensions. En application des résultats de la théorie de l'engagement issue de la psychologie sociale, les participants aux expériences ont la possibilité de s'engager sur l'honneur à donner des réponses sincères avant de participer à une enchère au second prix. Les résultats issus de traitements en valeur induite suggèrent que les enchères précédées d'un serment dominent toutes les autres conditions expérimentales (incitations montaires, hypothètique et serment avec incitations). Un second traitement applique ce même mécanisme à la révélation des préférences à l'égard de la protection des dauphins. La signature d'un serment solennel conduit les participants à prendre en compte à la fois leur contrainte budgétaire (ce qui discipline le comportement de révélation dans le haut de la distribution) et leur contrainte de participation (ce qui les conduit à déclarer des valeurs positives plutôt que des valeurs nulles destinées à se soustraire à l'enchère). Ces résultats sont robustes à la familiarité des participants à l'égard du mécanisme ...

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