Which vaccine attributes foster vaccine uptake? A cross-country conjoint experiment

Which foreign vaccine should the government purchase in a pandemic? Evidence from a survey experiment in the United States

BACKGROUND

For many countries confronting a future pandemic, the initial vaccines available will come from abroad. Public hesitancy to receive these foreign vaccines is important, as it may create an incentive for governments to forego procuring them for public use. We investigate the influence of the vaccine's country of origin on public support for government procurement during the early stages of a pandemic and examine whether endorsements from the WHO can mitigate such biases.

METHODS

In the summer of 2023, we carried out a survey experiment of 1,110 U.S. residents where we asked respondents to rate their support for vaccine purchasing policies for 20 hypothetical vaccines (13,320 evaluations). We varied the vaccine's country of origin and its endorsement status from the WHO, while also randomizing other vaccine attributes.

RESULTS

Compared to foreign vaccines from countries Americans see favorable (e.g., Germany, the United Kingdom), those originating from less favorable countries (e.g., China, Russia), garnered lower support for government procurement. Our causal mediation analysis indicates that this country-of-origin effect is primarily driven by participants' sentiments toward the vaccine. Surprisingly, WHO endorsement does little to mitigate the effect of the vaccine's country of origin. These findings are consistent across various sample subsets and considerations of vaccine quality.

CONCLUSION

Our study advances previous work on vaccine country-of-origin effects by assessing its impact on policy preferences for procuring initial vaccines from overseas (as opposed to uptake intentions), identifying a mechanism by which vaccine favoritism occurs, and documenting that neither personal disease susceptibility nor vaccine quality fully mitigates country of origin effects. We conclude by discussing why the study of "vaccine diplomacy" ought to not only include interstate dynamics governing vaccine purchasing and availability but also consider vaccine-producing countries' more general reputations.

Updated beliefs and shaken confidence: evidence from vaccine hesitancy caused by experiencing "COVID arm"

BACKGROUND

Public health depends largely on people's knowledge, beliefs, or behaviors regarding their health and medical treatments. Although works based on the health belief model have shown that public beliefs about medical treatments affect willingness to take the treatments, little is known about the effects of changes in beliefs on attitudes toward treatment. How one's past experiences relate to one's beliefs about a given medical treatment is worth considering.

METHODS

We implemented an online panel survey in February 2021 and March 2022 in Japan before and after COVID-19 vaccines were administered to the public within the country. We exploited delayed localized hypersensitivity reactions to COVID-19 vaccines, namely, "COVID arm", as an exogenous shock to investigate the relationship between past negative experiences and current beliefs about medical treatments or science. "COVID arm" was an unexpected side effect and thus likely caused updated beliefs about the vaccine. Out of the nonprobability sample of 15,000 respondents in the first wave in February 2021, 9,668 respondents also responded to the second wave conducted in March 2022. Outcome variables were whether experiencing "COVID arm" affected the respondents' 1) confidence in vaccine safety, 2) willingness to take the next dose of COVID-19 vaccines, 3) acknowledgment of the importance of vaccination, and 4) confidence in science. We measured the impact of experience with "COVID arm" on changes in the probability that survey respondents would respond affirmatively to questions posed about the issues listed above.

RESULTS

Experiencing "COVID arm" significantly lowered confidence in the safety of vaccination by 4.3 percentage points, which was approximately 6% of the sample mean for the first wave, and lowered the probability of taking a second dose of the COVID-19 vaccine by 1.5 percentage points. These adverse impacts were observed after conditioning background characteristics and prior confidence in vaccination. Experiencing "COVID arm" affected neither the acknowledged importance of vaccination nor confidence in science in a statistically significant way.

CONCLUSIONS

An unexpected and uncomfortable shock regarding beliefs about a treatment decreases willingness to take the treatment. An appropriate public health policy should account for this effect.

TRIAL REGISTRATION

The survey was preregistered with the American Economic Association's RCT Registry (Fukai et al., 2022).

The political component of COVID-19 vaccine choice: Results from a conjoint experiment

OBJECTIVES

Prior research highlights the role of efficacy, vaccine safety, and availability in vaccine hesitancy. Research is needed to better understand the political driving forces behind COVID-19 vaccine uptake. We examine the effects of the origin of a vaccine, and approval status within the EU on vaccine choice. We also test if these effects differ by party affiliation among Hungarians.

STUDY DESIGN

We use a conjoint experimental design to assess multiple causal relationships. Respondents choose between two hypothetical vaccine profiles randomly generated from 10 attributes. The data were gathered from an online panel in September 2022. We applied a quota for vaccination status and party preference. Three hundred twenty-four respondents evaluated 3888 randomly generated vaccine profiles.

METHODS

We analyse the data using an OLS estimator with standard errors clustered by respondents. To further nuance our results, we test for task, profile, and treatment heterogeneity effects.

RESULTS

By origin, respondents prefer German (MM 0.55; 95% CI 0.52-0.58) and Hungarian (0.55; 0.52-0.59) vaccines over US (0.49; 0.45-0.52) and Chinese vaccines (0.44; 0.41-0.47). By approval status, vaccines approved by the EU (0.55, 0.52-0.57) or pending authorization (0.5, 0.48-0.53) are preferred over unauthorised ones (0.45, 0.43-0.47). Both effects are conditional on party affiliation. Government voters especially prefer Hungarian vaccines (0.6; 0.55-0.65) over others.

CONCLUSIONS

The complexity of vaccination decisions calls for the usage of information shortcuts. Our findings demonstrate a strong political component that motivates vaccine choice. We demonstrate that politics and ideology have broken into fields of individual-level decisions such as health.

Phage therapy and the public: Increasing awareness essential to widespread use

Today, the antimicrobial resistance (AMR) crisis is shaping a world where previously treatable infections can kill. This has revitalised the development of antibiotic alternatives, such as phage therapy. The therapeutic use of phages, viruses that infect and kill bacteria, was first explored over a century ago. However, most of the Western world abandoned phage therapy in favour of antibiotics. While the technical feasibility of phage therapy has been increasingly investigated in recent years, there has been minimal effort to understand and tackle the social challenges that may hinder its development and implementation. In this study, we assess the UK public's awareness, acceptance, preferences and opinions regarding phage therapy using a survey, fielded on the Prolific online research platform. The survey contained two embedded experiments: a conjoint and framing experiment (N = 787). We demonstrate that acceptance of phage therapy among the lay public is already moderate, with a mean likelihood of acceptance of 4.71 on a scale of 1 (not at all likely to accept phage therapy) to 7 (very likely to accept phage therapy). However, priming participants to think about novel medicines and antibiotic resistance significantly increases their likelihood of using phage therapy. Moreover, the conjoint experiment reveals that success and side effect rate, treatment duration, and where the medicine has been approved for use has a statistically significant effect on participants' treatment preferences. Investigations altering the framing of phage therapy, to highlight positive and negative aspects, reveal a higher acceptance of the treatment when described without using perceived harsh words, such as "kill" and "virus". Combined, this information provides an initial insight into how phage therapy could be developed and introduced in the UK to maximise acceptance rate.

Investigating how historical legacies of militarized violence can motivate COVID-19 vaccine hesitancy: Evidence from global dyadic survey

BACKGROUND

In almost all countries, COVID-19 vaccines available for public use are produced outside of that country. Consistent with recent social science research, we hypothesize that legacies of violent conflict from vaccine-producing against vaccine-consuming countries may motivate vaccine hesitancy among people in targeted countries that purchase vaccines produced by the erstwhile aggressor.

METHODS

Our analyses draw on data from the Correlates of War project and a large, representative survey of 18,291 adults that asked respondents in 16 countries to self-report their attitudes toward COVID-19 vaccines originating from 12 potential vaccine-producing countries in December 2020 (184 country-pairs, 208,422 ratings). For the main analysis, we used random-effect linear probability models and turned to Bayesian Model Averaging to probe the robustness of the main findings.

RESULTS

We demonstrate that elevated levels of historical violence between vaccine-producing and vaccine-consuming countries are associated with increased negative feelings toward a COVID-19 vaccine produced by the vaccine producer.

CONCLUSION

Global vaccine hesitancy may result, at least in part, from public perceptions of historical conflict between vaccine-producing and vaccine-consuming countries. These results can help public health practitioners better preempt and adjust for cross-national vaccine resistance.

The citizen preferences-positive externality trade-off: A survey study of COVID-19 vaccine deployment in Japan

Objective

Medicine is a scarce resource and a public good that benefits others by bettering patients’ health. COVID-19 vaccines in shortage are, 1) a scarce resource and 2) a public good with the positive externality of building herd immunity. These features are expected to drive citizens’ attitudes in opposite directions, exclusionist and inclusionist, respectively. Scarcity would drive citizens’ exclusionism, while the positive externality might mitigate exclusionism.

Setting and design

We recruited 15,000 Japanese adults and asked them to rank, in the context of a COVID-19 vaccine shortage, the deservingness of hypothetical vaccine recipients who differed according to 1) citizenship status, 2) visa type and duration of stay (if foreign), 3) occupation, 4) age, 5) whether they lived with a child, and 6) whether they lived with an elderly individual. Citizenship options were Japanese, Chinese, Taiwanese, South Korean, American, or European. The occupations were healthcare, education, other employed, self-employed, or not employed. The 6 attributes were randomly combined, and respondents were shown 3 hypothetical vaccine recipients: one was Japanese, and the others were foreigners.

Treatments

First, through a conjoint design, we created hypothetical vaccine recipients whose attributes were randomized except for the benchmark citizenship, Japanese national. Second, we randomly presented two scenarios for vaccination payments: 1) billed at cost or 2) fully subsidized by the government.

Results

1) Whether the vaccines were billed at cost or fully subsidized did not affect the rankings of deservingness. 2) Japanese citizenship was prioritized. 3) The penalty for being a foreigner was higher for individuals from nations with which Japan has geopolitical tensions. 4) Working in health or education reduced the penalty on foreigners, indicating that the positive externality related to occupation amplifies the positive externality associated with vaccination and mitigates exclusionist attitudes.

Conclusions

The positive occupational externalities that amplify the positive externality of vaccination substantially allay the foreigner penalty.

Vaccine nationalism among the public: A cross-country experimental evidence of own-country bias towards COVID-19 vaccination

What types of vaccines are citizens most likely to accept? We argue that citizens' identification with their nation may lead them to prefer vaccines developed and produced within their national borders, to the exclusion and/or detriment of vaccines from other nations. We administered a conjoint experiment requesting 15,000 adult citizens across 14 individual countries from around the world to assess 450,000 profiles of vaccines that randomly varied on seven attributes. Beyond vaccine fundamentals such as efficacy rate, number of doses, and duration of the protection, we find that citizens systematically favor vaccines developed and produced in their own country of residence. The extent of preference in favor of vaccines developed and produced within the national borders is particularly large among citizens who identify more strongly with their nation, suggesting nationalism plays a role in explaining the bias in favor of vaccines developed and produced locally. This public opinion bias on vaccine preferences has significant theoretical and practical implications.