Determinants of COVID-19 vaccine preference: A survey study in Japan

Association between Gross National Income per capita and COVID-19 vaccination coverage: a global ecological study

BACKGROUND

Coronavirus 2019 (COVID-19) pandemic has claimed over six million lives and infected more than 650 million people globally. Public health agencies have deployed several strategies, including rolling out vaccination campaigns to curb the pandemic, yet a significant proportion of the global population has not received the COVID-19 vaccine. We assessed differences in COVID-19 vaccination coverage by Gross National Income (GNI) per capita of WHO members (i.e., countries, areas, and territories, n = 192) and by WHO member regions (n = 6).

METHODS

Using an ecological study design, we analyzed publicly available data from the WHO website merged with the World Bank's GNI per capita data. We included a total of 192 WHO members and six WHO regions in the analysis. We utilized negative binomial regression to assess the associations between the GNI per capita and COVID-19 vaccination coverage (cumulative number of persons fully vaccinated and/or received at least one dose of the vaccine per 100 population), and ANOVA test to assess the differences in vaccination coverage per WHO regions.

RESULTS

Low GNI per capita WHO members had significantly lower full vaccination coverage (aRR 0.30, 95% CI 0.22-0.40) compared to high GNI per capita WHO members. These members were also 66% less likely to receive at least one dose of the vaccine (aRR 0.34, 0.26-0.44) relative to high GNI per capita WHO members. Africa region had a significantly lower fully vaccination coverage (aRR 0.71, 95% CI 0.36-0.54) and received at least one dose of the COVID-19 vaccine (aRR 0.78, 95% CI 0.62-0.99) than Europe region. Conversely, the Western Pacific region had significantly higher fully vaccination coverage (aRR 1.40 95% CI 1.12-1.74) and received at least one dose of COVID-19 vaccines (aRR 1.40 95% CI 1.14-1.73) relative to European region.

CONCLUSION

WHO members with low GNI per capita and the African region reported significantly lower COVID-19 vaccination coverage than those with high GNI per capita or other regions. Efforts to strengthen and promote COVID-19 vaccination in low-income WHO countries and African region should be scaled up.

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).

Estimation of Intangible Costs for Factors Associated with Oral Antiviral Drugs for COVID-19 Treatment: A Conjoint Analysis in Japan

INTRODUCTION

During the recent coronavirus disease 2019 (COVID-19) pandemic, preferences for factors associated with vaccines have been evaluated. Three oral antiviral drugs have been approved in Japan for patients with mild-to-moderate I COVID-19 symptoms. Although preferences for the drugs may also depend on various factors, these have not been fully evaluated.

METHODS

A conjoint analysis was performed based on an online survey in August 2022 to estimate the intangible costs of factors associated with oral antiviral drugs for COVID-19. Respondents were individuals aged 20-69 across Japan. The attributes included the company (Japanese/foreign) that developed the drug, formulation and size of the drug, frequency of administration per day, number of tablets/capsules per dose, number of days until no longer infectious to others, and out-of-pocket expenses. A logistic regression model was applied to estimate the utility of each level for each attribute. The intangible costs were calculated by comparing the utility to the out-of-pocket attribute.

RESULTS

Responses were collected from 11,303 participants. The difference between levels was the largest for companies that developed a drug; the intangible costs were JPY 5390 higher for the foreign company than for the Japanese company. The next largest difference was in the number of days until one is no longer infectious. For the same formulation, the intangible cost was lower for small sizes than large sizes. For similar-sized tablets and capsules, the intangible cost was lower for tablets than capsules. These tendencies were similar regardless of COVID-19 infection history and the presence of risk factors for severe COVID-19 in the respondents.

CONCLUSION

Intangible costs for factors associated with oral antiviral drugs among the Japanese population were estimated. The results may change as the number of people with a history of COVID-19 infection increases and significant progress is made regarding treatments.

The COVID-19 vaccination decision-making preferences of elderly people: a discrete choice experiment

COVID-19 is a continuing threat to global public health security. For elderly people, timely and effective vaccination reduces infection rates in this group and safeguards their health. This paper adopted an offline Discrete Choice Experiment (DCE) to research the preference for COVID-19 vaccination amongst Chinese adults aged 50 years and above. Through multinomial logistic regression analysis, our DCE leverages five attributes-the risk of adverse reactions, protective duration, injection doses, injection period, and effectiveness-each of which is split into three to four levels. The risk of adverse reaction and the protective duration were demonstrated to be determinants of vaccination preference. Moreover, it was found that socio demographic factors like region, self-health assessment and the number of vaccinated household members can strengthen or weaken the effects of vaccine attributes. In conclusion, the preferences of the elderly population should be considered when developing COVID-19 vaccination programs for this population in China. Accordingly, the results may provide useful information for policymakers to develop tailored, effectively vaccination strategies.

Effect of vaccination patterns and vaccination rates on the spread and mortality of the COVID-19 pandemic

Objectives

Acquiring herd immunity through vaccination is the best way to curb the COVID-19 infection. Many countries have attempted to reach the herd immunity threshold as early as possible since the commencement of vaccination at the end of 2020. The purpose of this study is to (1) examine whether the pattern of vaccination rates affects the spread of COVID-19 and the consequent mortality and (2) investigate the level of cumulative vaccination rates that can begin to have an impact on reducing the spread and mortality of the pandemic.

Methods

This study selected 33 countries with higher vaccination rates as its sample set, classifying them into three groups as per vaccination patterns.

Results

The results showed that vaccination patterns have a significant impact on reducing spread and mortality. The full-speed vaccination pattern showed greater improvement in the spread of the COVID-19 pandemic than the other two patterns, while the striving vaccination pattern improved the most in terms of mortality. Secondly, the spread and mortality of the COVID pandemic started to significantly decline when the average cumulative vaccination rate reached 29.06 doses per 100 people and 7.88 doses per 100 people, respectively.

Conclusion

The study highlights the important role of vaccination patterns and the VTMR in reducing the epidemic spread and mortality.

The Willingness of Parents to Vaccinate Their Children Aged from Five to under Twelve Years with COVID-19 Vaccines between February and March 2022 in Vietnam

The current study used data surveyed with 5357 parents/guardians (parents would be used to represent both 'parents' and 'guardians' hereafter) between February and March 2022 in Vietnam to examine their willingness to vaccinate their children with current COVID-19 vaccines. It applied the multinomial logistic regression model to examine the association between the willingness of parents and selected influential factors. In addition, the reasons that made parent hesitant or unwilling to vaccinate their children were investigated. Moreover, it identified parents' preferences for vaccine origins. Approximately, 75.4% of the parents were willing, 21.3% were hesitant and 3.3% were unwilling to vaccinate their children. The most common reasons that made the parents hesitant or unwilling to vaccinate their children were their concerns about the vaccine safety, efficacy and immunity. The most and the second most preferred vaccines were those developed/originated in the US and EU, respectively. Parents who were more likely to vaccinate their children included those whose children were insured, who regularly vaccinated their children, who belonged to the vaccine priority groups, who possessed sufficient knowledge about the ways to prevent the virus or about the herd immunity, and who perceived that their children might be infected with the virus and whose children were afraid of needles. Parents who were less likely to vaccinate their children included those who were the family main income source, who had savings, and who had tertiary education or higher.

The Willingness to get Vaccinated Against SARS-CoV-2 Virus among Southeast Asian Countries: Does the Vaccine Brand Matter?

The current study uses data surveyed with 2,500 respondents during August and September 2021 in Vietnam, Indonesia, the Philippines and Malaysia to examine the willingness to get vaccinated against SARS-CoV-2 virus with six COVID-19 vaccines. The willingness to get vaccinated varies according to the vaccine brands and selected influential factors. Particularly, the percentage of respondents who are willing to get vaccinated with Pfizer, Moderna and AstraZeneca dominates that of those who are willing to get vaccinated with Sinopharm, Janssen and Sputnik V vaccines. Results generated from the binary logistic regressions show that the impact of the selected influential factors on the willingness to get vaccinated varies in terms of magnitude and direction, and depending on the vaccine brands. The results indicate that additional scientific evidence on the efficacy and safety of the vaccines is essential for the respondents to decide whether to vaccinate or not. Such evidence can be made available in multiple formats and provided through appropriate channels and vaccination communication campaigns.

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.

A Systematic Investigation of American Vaccination Preference via Historical Data

While COVID-19 vaccines are generally available, not all people receive vaccines. To reach herd immunity, most of a population must be vaccinated. It is, thus, important to identify factors influencing people’s vaccination preferences, as knowledge of these preferences allows for governments and health programs to increase their vaccine coverage more effectively. Fortunately, vaccination data were collected by U.S. Census Bureau in partnership with the CDC via the Household Pulse Survey (HPS) for Americans. This study presents the first analysis of the 24 vaccination datasets collected by the HPS from January 2021 to May 2022 for 250 million respondents of different ages, genders, sexual orientations, races, education statuses, marital statuses, household sizes, household income levels, and resources used for spending needs, and with different reasons for not receiving or planning to receive a vaccine. Statistical analysis techniques, including an analysis of variance (ANOVA), Tukey multiple comparisons test, and hierarchical clustering (HC), were implemented to analyze the HPS vaccination data in the R language. It was found that sexual orientation, gender, age, and education had statistically significant influences on the vaccination rates. In particular, the gay/lesbian group showed a higher vaccination rate than the straight group; the transgender group had a lower vaccination rate than either the female or the male groups; older respondents showed greater preference for vaccination; respondents with higher education levels also preferred vaccination. As for the other factors that were not significant enough to influence vaccinations in the ANOVA, notable trends were found. Asian Americans had higher vaccination rates than other races; respondents from larger household sizes had a lower chance of getting vaccinated; the unmarried group showed the lowed vaccination rate in the marital category; the respondents depending on borrowed money from the Supplemental Nutrition Assistance Program (SNAP) showed a lower vaccination rate than people with regular incomes. Concerns regarding the side-effects and the safety of the vaccines were the two major reasons for vaccination hesitance at the beginning of the pandemic, while having no trust in the vaccines and no trust in the government became more common in the later stage of the pandemic. The findings in this study can be used by governments or organizations to improve their vaccination campaigns or methods of combating future pandemics.

Association between Adverse Reactions to the First and Second Doses of COVID-19 Vaccine

This study investigated the frequency of adverse reactions to COVID-19 vaccines in Japan and the impact of first-dose adverse reactions on second-dose adverse reactions. Individuals who received an mRNA COVID-19 vaccine at our center in March or April 2021 were included. Data were collected using questionnaires. The main factors were age (<40, 40−59, and >60 years), sex, underlying disease, and first-dose adverse reaction. The primary outcomes were incidence of local and systemic adverse reactions (ARs) attributable to the vaccine. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Among 671 participants, 90% experienced local or systemic ARs. An AR to the first dose was associated with a significantly increased risk of an AR to the second dose (OR: 49.63, 95% CI: 21.96−112.16). ARs were less common among men than among women (OR: 0.36, 95% CI: 0.17−0.76). Local ARs were less common among those aged 60 years or older (OR: 0.35, 95% CI: 0.18−0.66), whereas systemic ARs were more common among those aged under 40 years. Information on ARs to the first dose is important for healthcare providers and recipients when making vaccination decisions.

Trusting COVID-19 vaccines as individual and social goal

Trust in vaccines and in the institutions responsible for their management is a key asset in the global response to the COVID-19 pandemic. By means of a structured multi-scales survey based on the socio-cognitive model of trust, this study investigates the interplay of institutional trust, confidence in COVID-19 vaccines, information habits, personal motivations, and background beliefs on the pandemic in determining willingness to vaccinate in a sample of Italian respondents (N = 4096). We observe substantial trust in public institutions and a strong vaccination intention. Theory-driven structural equation analysis revealed what factors act as important predictors of willingness to vaccinate: trust in vaccine manufacturers (which in turn is supported by trust in regulators), collectivist goals, self-perceived knowledgeability, reliance on traditional media for information gathering, and trust in institutional and scientific sources. In contrast, vaccine hesitancy, while confined to a minority, is more prominent in less educated and less affluent respondents. These findings can inform institutional decisions on vaccine communication and vaccination campaigns.

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

Why do people prefer one particular COVID-19 vaccine over another? We conducted a pre-registered conjoint experiment (n = 5,432) in France, Germany, and Sweden in which respondents rated the favorability of and chose between pairs of hypothetical COVID-19 vaccines. Differences in effectiveness and the prevalence of side-effects had the largest effects on vaccine preferences. Factors with smaller effects include country of origin (respondents are less favorable to vaccines of Chinese and Russian origin), and vaccine technology (respondents exhibited a small preference for hypothetical mRNA vaccines). The general public also exhibits sensitivity to additional factors (e.g. how expensive the vaccines are). Our data show that vaccine attributes are more important for vaccine preferences among those with higher vaccine favorability and higher risk tolerance. In our conjoint design, vaccine attributes–including effectiveness and side-effect prevalence–appear to have more muted effects among the most vaccine hesitant respondents. The prevalence of side-effects, effectiveness, country of origin and vaccine technology (e.g., mRNA vaccines) determine vaccine acceptance, but they matter little among the vaccine hesitant. Vaccine hesitant people do not find a vaccine more attractive even if it has the most favorable attributes. While the communication of vaccine attributes is important, it is unlikely to convince those who are most vaccine hesitant to get vaccinated.

COVID-19 Vaccine Acceptance among ASEAN Countries: Does the Pandemic Severity Really Matter?

The current study uses data surveyed between August and September 2021 in four ASEAN (Association of South East Asian Nations) countries to identify drivers of COVID-19 vaccine acceptance with different levels of the pandemic severity. It also examines the impact of the drivers on vaccine acceptance. The results show that the number of respondents who accept vaccines significantly dominates that of those who do not. In addition, the number of respondents who get the vaccine if the pandemic becomes more severe dominates that of those if it becomes less severe. Results generated from the logistic regressions show that the impact of the drivers on the COVID-19 vaccine acceptance with different levels of the pandemic severity varies in terms of magnitude and direction. Practical recommendations are made based on the findings.

Public Opinion and Sentiment Before and at the Beginning of COVID-19 Vaccinations in Japan: Twitter Analysis

Background

COVID-19 vaccines are considered one of the most effective ways for containing the COVID-19 pandemic, but Japan lagged behind other countries in vaccination in the early stages. A deeper understanding of the slow progress of vaccination in Japan can be instructive for COVID-19 booster vaccination and vaccinations during future pandemics.

Objective

This retrospective study aims to analyze the slow progress of early-stage vaccination in Japan by exploring opinions and sentiment toward the COVID-19 vaccine in Japanese tweets before and at the beginning of vaccination.

Methods

We collected 144,101 Japanese tweets containing COVID-19 vaccine-related keywords between August 1, 2020, and June 30, 2021. We visualized the trend of the tweets and sentiments and identified the critical events that may have triggered the surges. Correlations between sentiments and the daily infection, death, and vaccination cases were calculated. The latent dirichlet allocation model was applied to identify topics of negative tweets from the beginning of vaccination. We also conducted an analysis of vaccine brands (Pfizer, Moderna, AstraZeneca) approved in Japan.

Results

The daily number of tweets continued with accelerating growth after the start of large-scale vaccinations in Japan. The sentiments of around 85% of the tweets were neutral, and negative sentiment overwhelmed the positive sentiment in the other tweets. We identified 6 public-concerned topics related to the negative sentiment at the beginning of the vaccination process. Among the vaccines from the 3 manufacturers, the attitude toward Moderna was the most positive, and the attitude toward AstraZeneca was the most negative.

Conclusions

Negative sentiment toward vaccines dominated positive sentiment in Japan, and the concerns about side effects might have outweighed fears of infection at the beginning of the vaccination process. Topic modeling on negative tweets indicated that the government and policy makers should take prompt actions in building a safe and convenient vaccine reservation and rollout system, which requires both flexibility of the medical care system and the acceleration of digitalization in Japan. The public showed different attitudes toward vaccine brands. Policy makers should provide more evidence about the effectiveness and safety of vaccines and rebut fake news to build vaccine confidence.

Variations in Early-Stage Responses to Pandemics: Survey Evidence from the COVID-19 Pandemic in Japan

During the initial phase of pandemics, swift behavioral responses by individuals, such as social distancing, can temper the speed and magnitude of further infections. However, individual choices in this period are often made in the absence of reliable knowledge and coordinated policy interventions, producing variation in protective behaviors that cannot be easily deduced from that in later periods. Using unique monthly panel survey data, we examine variations in the association between changes in infections and risky behavior, particularly the frequencies of face-to-face conversations and dining out, between January to March 2020. We find that the increase in confirmed cases is negatively associated with the likelihood of these behaviors. However, high school graduates are less responsive than university graduates. We provide evidence that this can be attributed to their lower perception of infection risk, while we cannot fully rule out the roles of income opportunity costs. These results point to the benefits of interventions incorporating nudges to raise individuals’ risk perceptions during the initial phase of pandemics. We also discuss the potential efficacy of such interventions in later periods of pandemics.

Differences in COVID-19 Vaccine Acceptance, Hesitancy, and Confidence between Healthcare Workers and the General Population in Japan

Little is known about the differences in coronavirus disease (COVID-19) vaccine acceptance and hesitancy between the general population and healthcare workers in Japan. To compare these differences, a nationwide web-based cross-sectional survey was conducted on 19 January 2021, shortly before the initiation of COVID-19 vaccinations in Japan. A total of 6180 men and women aged 20-69 years and 1030 healthcare workers aged 20-69 years were enrolled. Data on COVID-19 vaccine acceptance, basic characteristics, including socioeconomic factors, and confidence in immunization in general were collected. COVID-19 vaccine acceptance was also evaluated under hypothetical vaccine effectiveness and adverse event frequencies. Factors associated with vaccine hesitancy were examined using multinomial logistic regression analysis. The COVID-19 vaccine acceptance rate was 48.6% among the general population and was lower among nurses (45.5%) and medical clerks (40.7%). Women and young adults had significantly higher COVID-19 vaccine hesitancy odds ratios, and current smokers had significantly lower odds ratios. The frequency of adverse events was a COVID-19 vaccine hesitancy factor. Even if these factors were adjusted, COVID-19 vaccine hesitancy among nurses was 1.4 times higher than that among the general population. Thus, interventions to improve health literacy and vaccine hesitancy among the general population and healthcare workers, especially nurses, are needed.

COVID-19 Vaccine Hesitancy among Italian University Students: A Cross-Sectional Survey during the First Months of the Vaccination Campaign

Achieving high levels of vaccination coverage against COVID-19 may be hindered by vaccine hesitancy. We quantified over time the prevalence of COVID-19 vaccine hesitancy among university students, investigated its determinants, and analyzed student attitudes, risk perceptions and compliance with preventive measures. The survey was administered online from 1 March to 30 June 2021. A multivariable logistic regression model was built to identify predictors of hesitancy. Overall, we collected 5369 questionnaires that were grouped into three survey periods (March, April-May, and May-June). The response rate ranged from 81.2% to 76.4%, whereas vaccine hesitancy ranged from 22% to 29%. Multivariable analysis showed that April-May participants had higher odds of hesitancy than March respondents. Other positive predictors were being male, not being a healthcare student, having a lower academic level, and not disclosing a political position. Conversely, higher levels of perceived COVID-19 severity, concern for the emergency, confidence in vaccine safety and effectiveness, and self-reported adherence to mask wearing indoors and outdoors were negatively associated with hesitancy. We found that vaccine hesitancy changed over time and in relation to several factors. Strategies aimed at increasing the students' awareness and engagement, restoring confidence in health authorities, and limiting disinformation around the vaccines should be devised.