key: cord-0303747-f7nd8dir authors: Okamoto, S.; Kamimura, K.; Komamura, K. title: COVID-19 vaccine hesitancy and vaccine passports: Vaccination or restriction? date: 2021-09-22 journal: nan DOI: 10.1101/2021.09.15.21263559 sha: c1a7d803cc044013ba5e10069cd10d2f0cd85b5a doc_id: 303747 cord_uid: f7nd8dir Objectives: While the development of vaccines against the novel coronavirus (COVID-19) brought the hope of establishing herd immunity, which might help end the global pandemic, vaccine hesitancy can hinder the progress towards herd immunity. In this study, we assess the determinants of vaccine hesitancy, reasons for hesitation, and effectiveness of vaccine passports in relaxing public health restrictions. Methods: Through an online survey that includes a conjoint experiment of a demographically representative sample of 5,000 Japanese adults aged 20-74, we assess the determinants of vaccine hesitancy, reasons for hesitation, and effectiveness of hypothetical vaccine passports. Results: We found that about 30% of respondents did not intend to vaccinate or have not yet decided, with major reasons for vaccine hesitancy being related to concerns about the safety and side effects of the vaccine. In line with previous findings, younger age, lower socioeconomic status, and psychological factors such as weaker COVID-19 fear were associated with vaccine hesitancy. The easing of public health restrictions such as travel, wearing face masks, and dining out at night was associated with an increase in vaccine acceptance by 4-10%. Conclusion: Vaccine hesitancy can be reduced by mitigating the concerns about vaccine safety and side effects, as well as by relaxing public health restrictions. However, the feasibility of vaccine passports needs to be sufficiently assessed, taking the ethical issues of passports and the public health impacts of the relaxation of restrictions into careful consideration. After a period when nations have managed to curb the spread of the new coronavirus disease , mainly by non-pharmaceutical interventions such as containment and closure policies, the development of COVID-19 vaccines brought hope that the pandemic may end soon. Although the degree and duration of vaccine efficacy as well as the efficacy against new virus variants remain unconfirmed (Hacisuleyman et al., 2021) , widespread vaccination can contribute to establishing herd immunity against COVID-19. While the required proportions of individuals with immunity could vary by country (e.g. due to demographic structure and frequency of human contact), it is estimated that approximately 70% of the population needs immunity to achieve herd immunity against COVID-19, which would require more than 30 million deaths worldwide due to natural infection (Randolph & Barreiro, 2020) . Therefore, global vaccination is a necessary step to end the pandemic. However, the vaccine hesitancy, defined as a 'delay in acceptance or refusal of vaccines despite availability of vaccine services' by a working group advising the World Health Organization (MacDonald & Sage Working Group on Vaccine Hesitancy, 2015), can hinder achieving herd immunity. The findings of systematic reviews and meta-analyses suggest that the vaccine acceptance rates are around 60-75% but show large discrepancies across regions, months of study, and whether an answer of 'unsure' is available to survey respondents (Robinson et al., 2021; Wang et al., 2021) . Together with the global disparities in vaccine availability for COVID-19, full vaccination rates are considerably low, and only about a third of the world population had received at least one dose of a vaccine against COVID-19 by August 2021 (Mathieu et al., 2021) . While this low vaccine uptake may be due to many reasons, including factors other than individual preferences, such as system failures, it is important to identify why people are reluctant to vaccinate to establish herd immunity by avoiding preventable vaccine hesitancy. Whether an individual accepts vaccination is a consequence of a complex decision-making process, which occurs on the continuum between complete acceptance and refusal (Dube et al., 2013; MacDonald & Sage Working Group on Vaccine Hesitancy, 2015) . The above-mentioned working group developed the 'three Cs vaccine hesitancy model', which comprises confidence, complacency, and convenience, indicating that historic, socio-cultural, environmental, health system/institutional, economic or political factors, as well as personal perception and vaccine/vaccination characteristics matter towards vaccine hesitancy. Moreover, from a utilitarian perspective, voluntary vaccinations can deviate from the social optimum due to the positive externalities of vaccinated individuals; hence, Pigouvian subsidies, external regulations, or strategies to improve vaccine awareness is needed, depending on the nature of vaccine-preventable diseases and vaccines (Bauch et al., 2003; Chen & Toxvaerd, 2014; Liu et al., 2012) . Therefore, it is important to understand the reasons of those who tend not to accept a COVID-19 vaccine, in addition to strategies to raise the vaccination rates. In the following section, we review the literature on the determinants of COVID-19 vaccine hesitancy. (1) Socio-demographic factors Given the concerns of the increasing hesitancy towards COVID-19 vaccination, many empirical studies have hitherto assessed factors associated with COVID-19 vaccine hesitancy (Al-Amer et al., 2021; Sallam, 2021; Troiano & Nardi, 2021; Truong et al., . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10.1101 https://doi.org/10. /2021 2021; Wang et al., 2021) . These studies suggest that many empirical papers find that older people compared to their younger counterparts and men compared to women are more likely to accept a COVID-19 vaccine. Older people are susceptible to the disease and while men and women can decline vaccination for different reasons, the differences in perceived risks, efficacies, and knowledge may mediate these gender differences (Truong et al., 2021) . In addition to age and gender, educational attainment is identified as the most frequent predictor, with higher acceptance among people with higher education levels (Wang et al., 2021) . While highly educated individuals can be vaccine-hesitant because of the influence of social groups and other authorities, education may play an important role in understanding disease severity and vaccination benefits (Truong et al., 2021) . (2) Psychological and behavioural factors Vaccination is a consequence of one's utility maximisation, considering costs and benefits. Based on the health belief model, by modifying socio-demographic factors, individuals can decide whether to vaccinate as a reflection of their personal beliefs about a disease and its preventive measures, such as susceptibility, severity, benefits, barriers, and self-efficacy (Carico et al., 2021; Champion & Skinner, 2008) . A systematic review identifies that vaccine acceptance is higher among those with greater perceived risk, threat, vulnerability, and susceptibility to infection (Al-Amer et al., 2021; Troiano & Nardi, 2021) . Furthermore, the beliefs about the vaccine are predictors of vaccine hesitancy, including mistrust in its safety or efficacy and conspiracy beliefs, which can be induced by a low health literacy and negative information in the media (Al-Amer et al., 2021) . Together with one's perceptions regarding vaccines and infection, individual . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10.1101 https://doi.org/10. /2021 preferences matter for health-related decision-making, including vaccination (Cawley & Ruhm, 2011; Tsutsui et al., 2010) . Time preference affects one's vaccination intentions because individuals will benefit from the vaccination in the future, despite having to bear its present costs. Therefore, those discounted future benefits would lead them to decide not to vaccinate. Moreover, the attitudes toward risks are attributed to vaccination decision-making, that is, risk-averse individuals would feel conflicted between the risk of infection without vaccination and the vaccines' side effects. This would explain why younger people tend to be vaccine-hesitant, considering they are less likely to develop symptoms than their older counterparts (Poletti et al., 2021) and have more frequent side effects (Menni et al., 2021) . In addition to individuals' attributes and beliefs, vaccine characteristics are important determinants of vaccination intention, being highly relevant to individuals' perceptions and preference for vaccines. In particular, individuals prefer vaccines with higher efficacy, longer duration of disease protection, and safety (i.e. none or few adverse effects) (Al-Amer et al., 2021; Motta, 2021) . To increase vaccination rates, considering the determinants of vaccine hesitancy discussed above and vaccine characteristics, potential strategies would include removing the (mis)perceived effectiveness and risks of vaccination and infection, minimising the costs associated with vaccination (i.e. out-of-pocket payments and opportunity cost), and increasing the benefits of vaccination by providing various incentives. In fact, several approaches, such as communication, financial and nonfinancial incentives, and reminder-recall interventions, have been adopted and evaluated so far (Giles et al., 2014; Jarrett et al., 2015) . is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10.1101 https://doi.org/10. /2021 Vaccination campaign frameworks have also been adopted to increase the COVID-19 vaccination uptake. Aiming at a better understanding of the population for COVID-19 vaccines, public organisations disseminate information about the efficacy and safety of vaccines (Centers for Disease Control and Prevention, 2021b; World Health Organization, 2021a). Additionally, a study suggests that emphasising the benefits of vaccination and inducing feelings of vaccine ownership are useful (Ashworth et al., 2021; Dai et al., 2021) , thus suggesting the importance of information campaigns. In some countries, the convenience of vaccination locations is enhanced by providing these services within the areas of citizens' daily lives, such as train stations and supermarkets (Biesemans, 2021; The Metropolitan Transportation Authority, 2021). Furthermore, the incentives toward vaccination attract the attention of some policymakers (Volpp & Cannuscio, 2021) although their effectiveness remains inconclusive and may depend on how incentives are given (Kluver et al., 2021; Kreps et al., 2021; Serra-Garcia & Szech, 2021; Sprengholz et al., 2021; Walkey et al., 2021) . With remaining ethical concerns, vaccine passports, which fully or partially exempt vaccinated individuals from public health restrictions (Brown et al., 2021; Hall & Studdert, 2021; Osama et al., 2021; Phelan, 2020; Satria et al., 2021) , are considered in many regions. While only a limited number of related studies are available, the freedom allowed by vaccine passports can affect vaccine acceptance and preference (Eshun-Wilson et al., 2021; Kluver et al., 2021) . Despite the concern about `breakthrough infections', it would be worth considering the applicability of vaccine passports if and only if the passports largely contribute to achieving herd immunity against COVID-19 by increasing vaccine acceptance. . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10.1101 https://doi.org/10. /2021 Previous studies have documented the determinants of vaccine hesitancy by analysing the association of socio-demographic, psychological, and vaccine characteristics with vaccine intentions. Meanwhile, the evidence on how to increase COVID-19 vaccine acceptance remains scarce. In alignment with the policies in several regions, the evidence on communication strategies and the incentives for reducing vaccine hesitancy have gained increasing attention, as discussed above, while the effectiveness of vaccine passports in raising vaccine acceptance has been limited. While countries such as Israel, France, and Italy attempt to utilise vaccine passports, other countries may also consider similar schemes to return to a 'normal life'. If so, it is immensely important to accelerate herd immunity by reducing avoidable vaccine hesitancy, to which the benefits of the vaccine passports may contribute. Therefore, we assess the effectiveness of easing public health restrictions after vaccination by vaccine passports based on our analysis of a conjoint experiment. By decomposing the freedom factors allowed by the passport based on government regulations, we first evaluate an effective type of relaxation of public health restrictions to increase vaccine acceptance, which would be useful for health policymakers to design vaccine passports and deliver attractive information on the benefits of vaccination for vaccine-hesitant individuals. The data come from a demographically representative sample of 5,000 Japanese adults aged 20-74, which was conducted online during 21-23 July 2021. Survey respondents were recruited from registered panels of Cross Marketing Inc. To ensure that the survey is nationally representative regarding respondents' age and gender, . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10.1101 https://doi.org/10. /2021 we recruited respondents using quota sampling for each of the 14 age groups of the 2015 population census (i.e. age categories of 20s, 30s, 40s, 50s, 60s, and early 70s by gender). While we did not use regional quotas to recruit respondents, we addressed the potential non-representativeness arising from this by using weights for all analyses and estimated by population structures in each region. Specifically, we used eight categories for residential areas (i.e. Hokkaido, Tohoku, and Kanto, except for the Tokyo Metropolitan Area, Tokyo Metropolitan Area, Chubu, Kinki, Chugoku, Shikoku, and Kyusyu) and eleven categories for each five-year age group from 20 to 74. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10. 1101 (2) Independent variables To account for the factors associated with vaccine hesitancy, as indicated by previous findings (Al-Amer et al., 2021; Sallam, 2021; Troiano & Nardi, 2021; Truong et al., 2021; Wang et al., 2021) , we obtained demographic, socioeconomic, health-related, and psychological information on each respondent. The demographic and socioeconomic status of respondents included information on age, gender, co-resident family members, occupation, education, and income. Respondents living with members with chronic illnesses, aged 65 or over, and aged 11 or younger may be more likely to vaccinate because they are considered vulnerable to infection or not eligible for COVID-19 vaccination in Japan. In terms of occupation, we used three categories of essential healthcare workers, frontline essential workers, and other workers, following existing definitions (Centers for Disease Control and Prevention, 2021a). Educational attainment of respondents included three categories of high school or lower, junior college or vocational school, and university or higher. Income refers to annual household income, obtained as the median value in 19 ranges. We also used two health measures of self-rated health and depressive symptoms measured by the Kessler Psychological Distress Scale (K10), which have been validated by previous studies (Andrews & Slade, 2001; Chandola & Jenkinson, 2000; Kessler et al., 2002) . Higher scores indicate better health for the former scale, whereas lower scores indicate worse health for the latter. Finally, we used the following items to measure psychological and behavioural factors. Time and risk preferences, which relate to individuals' responses to uncertain risks of vaccination and infection, were measured in the following two . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10.1101/2021.09.15.21263559 doi: medRxiv preprint ways. The time preference was measured by the relative value of a larger later gain (13 months later) instead of a smaller immediate rewards (i.e. JPY 10,000 one month later) (Frederick et al., 2002) . The risk preference was obtained as the sum of the responses to seven questions on risk attitudes measured using a seven-point Likert scale (Meertens & Lion, 2008) , which indicate higher scores representing more riskloving. To measure respondents' perceived seriousness of COVID-19, we used the Fear of COVID-19 Scale (Ahorsu et al., 2020; Pakpour & Griffiths, 2020; Wakashima et al., 2020) . We defined respondents' numeracy as the number of correct answers to the same three questions proposed in a previous study (Lusardi & Mitchell, 2007) . To assess the determinants of vaccine hesitancy, the reasons for hesitating vaccination, and efficacies of the relaxation of public health restrictions on vaccine acceptance, we conducted the following three analyses. (1) Determinants of vaccine hesitancy We evaluated the association between vaccine hesitancy and its determinants, including demographic, socioeconomic, health, and psychological factors. In the base model, we analysed the association using a logit model with a dichotomised outcome (i.e. unwilling to vaccinate or undecided vs. willing to vaccinate or already vaccinated). To test the robustness of the results, we assessed the association using a three-level nominal outcome (unwilling to vaccinate vs. undecided vs. willing to vaccinate or already vaccinated). (2) Reasons for vaccine hesitancy . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 22, 2021. ; https://doi.org/10. 1101 We investigated the determinants of the reasons for vaccine hesitancy by analysing the association between demographic, socioeconomic, health, and psychological factors and each reason given by the individuals hesitating to vaccinate. We estimated the marginal effects of the factors for each reason using a logit model. (3) Conjoint analysis: vaccine passport To evaluate the association between the relaxation of public health restrictions by vaccine passports and vaccine acceptance, we utilised a conjoint experimental design (Hainmueller et al., 2017; Motta, 2021) . The conjoint experiment is useful in assessing the effects of varied attributes at different levels, reducing the number of necessary assignments using an orthogonal table. Using this design, in a hypothetical situation, we asked each respondent whether they would vaccinate, assuming that some or all four public health restrictions are relaxed. The four public health restrictions included travel across prefectures, dining out at night, joining gatherings and events, and going out without face masks, which correspond to government requests in Japan. Without the design, we would need to assign 16 (= 2 4 ) questions to assess each attribute of vaccine passports to each respondent; however, we reduced assignments by half, as shown in Table 1 . In the conjoint experiment, all respondents provided their vaccination intentions for each hypothetical vaccine passport. To account for potential non-random variance across respondents arising from repeated measures, we fitted populationaverage panel-data models using the method of generalised estimating equations (Schober & Vetter, 2018) , estimating robust standard errors, and considering logit . CC-BY 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint (Mathieu et al., 2021) , health professionals and older adults being prioritized. The proportion of the vaccinated population was almost identical to that of our sample (36.6%), indicating that our sample reflects the Japanese context well.