Vaccine hesitancy

This abstract is a report of the investigations by a transdisciplinary team working on the ‘Vaccine Confidence’ challenge (Supplement 1). Since their introduction, vaccines have been one of the most successful health interventions in medicine. Prior to vaccination programs against poliomyelitis, more than 350,000 cases of polio were reported annually worldwide, a number that decreased to just 33 reported cases in 20181. Additionally, between 2000 and 2017, the measles vaccination program is estimated to have prevented 21.1 million deaths.2 However, in 2018 more than 19 million children under one year of age did not receive the recommended WHO vaccines.3 A recent rise in anti-vaccine or vaccination-hesitant mentalities has led to decreasing vaccine coverage in several Western countries. The WHO identified three C’s as main determinants of vaccine hesitancy, namely Complacency, Convenience in accessing vaccines, and Confidence. However, the term ‘vaccine hesitancy’ tends to be interpreted as a lack of confidence in vaccines and vaccinations for various reasons. Nevertheless, the goal of vaccination is to reach herd immunity by reaching a high vaccination coverage (90‐95% vaccinated) to stop the circulation of vaccine preventable diseases. We wanted to give equal attention to the three C’s as they are equally important in reaching herd immunity. <target target-type="page-num" id="p-116"/>Therefore, we chose to present the problem as a challenge of ‘vaccine coverage,’ rather than ‘vaccine hesitancy’ or ‘vaccine confidence’. In order to understand the complexity of the problem, we have developed a systems map which relates different global factors that impact an individual’s vaccination decision-making, as well as their likelihood of receiving vaccinations (Supplement 2). To create this map we assembled the information for the variables and connections from literature studies of peer-reviewed articles and interviews with stakeholders, kept anonymous, in the field of vaccination or healthcare (Supplements 3 & 4). This approach was selected as it provides a wide perspective that allows academics, governmental authorities, and lawmakers to better assess the various factors that affect vaccine coverage, and how they are related. The work leading to the map was presented to the public at a symposium (Supplement 5). Our map identifies essential factors such as psychology, education, economy, vaccine technology, political and environmental sphere, sources of information, and healthcare in order to understand what governs vaccination coverage. The map emphasizes how various factors and determinants are often interrelated, as opposed to the isolated factors described in previous literature. We identified important discrepancies between developed and developing countries regarding the factors that drive vaccine-related decision-making and availability. The systems map could ultimately serve as a tool to better understand the multifaceted problem of suboptimal vaccination coverage. Vaccine hesitancy as a threat to vaccination coverage is a complex and wicked problem with many underlying contributing factors, as has been depicted in our systems map on vaccine coverage. Our systems map allows more in-depth insights, not only into which factors are contributing, but also into the relationship between factors. Solving the decrease in vaccination coverage will require different types of solutions which can be developed by using a transdisciplinary approach.

Effective Approaches to Combat Vaccine Hesitancy.

This study aims to evaluate maternal vaccine hesitancy and its associated factors. This is a cross-sectional study of a probabilistic sample of 450 mothers of children born in 2015, living in a Brazilian city, and who was, at the time of data collection, more than two years old. We used the tool proposed by the World Health Organization (10-item Vaccine Hesitancy Scale). To assess its structure, we performed, exploratory and confirmatory factor analyses. We performed linear regression models to evaluate the factors associated with vaccine hesitancy. The factor analysis showed two components for the vaccine hesitancy scale: lack of confidence in vaccines and risk perception of vaccines. High family income was associated with lower vaccine hesitancy (greater confidence in vaccines and lower risk perception of vaccines), while the presence of other children, regardless of birth order, in the family was associated with lower confidence in vaccines. A good rapport with health professionals, willingness to wait for the vaccination and the getting vaccinated through campaigns were associated with greater confidence in vaccines. The deliberate delay or decision not to vaccinate their children and previous experience with adverse reactions to the vaccine were associated with lower confidence in vaccines and greater risk perception of vaccines. Health care providers, especially nurses, play a relevant role to address vaccine hesitancy, guiding vaccination through a trustworthy rapport.

This study aimed to understand vaccine hesitancy and confidence toward the COVID-19 vaccines among Latino adults in Arizona. Latinos (n = 71) aged 18 years or older who resided in Arizona participated in 14 focus groups between February and June 2021. Theoretical thematic analysis was used to examine drivers of these two behaviors, namely, vaccine hesitancy and confidence toward the COVID-19 vaccines, using the COM-B model, comprising capability, opportunity, and motivation factors that generate a behavior. Vaccine hesitancy stemmed from the need for vaccine information (capability factor) and fear of the vaccines, religious beliefs, and perceived barriers stemming from government mistrust (motivation factors). Vaccine confidence arose from trust in science and doctors (capability factor), and a fear of getting sick, protection against COVID-19, getting vaccinated as a civic duty, and a desire to return to normal life (motivation factors). The influence of opportunity factors, such as having access to vaccinations, were not discussed as contributing to vaccine confidence or hesitancy. As predicted by the COM-B model, factors reflecting capabilities and motivations contributed to vaccine hesitancy and confidence, all of which need to be considered in public health messaging. These factors can be targeted to facilitate efforts to promote vaccine uptake and reduce the spread of COVID-19.

In Tanzania, the One by One: Target COVID-19 campaign was launched nationally in July 2022 to address the prevalent vaccine hesitancy and lack of confidence in COVID-19 vaccines. The campaign mobilized social media influencers and viral content with the ultimate goal of increasing COVID-19 vaccine uptake in the country. The objective of this study was to empirically assess the impact of the campaign on three outcomes: vaccine confidence, vaccine hesitancy, and vaccination status. Using programmatic data collected through an online survey before and after the campaign, we conducted a difference-in-difference (DiD) analysis and performed a crude, adjusted, and propensity score-matched analysis for each study outcome. Lastly, to observe whether there was any differential impact of the campaign across age groups, we repeated the analyses on age-stratified subgroups. Data included 5,804 survey responses, with 3,442 and 2,362 responses collected before and after the campaign, respectively. Although there was only weak evidence of increased COVID-19 vaccine confidence in the campaign-exposed group compared to the control group across all age groups, we observed a differential impact among different age groups. While no significant change was observed among young adults aged 18-24 years, the campaign exposure led to a statistically significant increase in vaccine confidence (weighted/adjusted DiD coefficient = 0.76; 95% CI: 0.06, 1.5; p-value = 0.034) and vaccination uptake (weighted/adjusted DiD coefficient = 1.69.; 95% CI: 1.02, 2.81; p-value = 0.023) among young adults aged 25-34 years. Among adults aged 35 years and above, the campaign exposure led to a significant decrease in vaccine hesitancy (weighted/adjusted DiD coefficient = -15; 95% CI: -21, -8.3; p-value<0.001). The social media campaign successfully improved vaccine hesitancy, confidence, and uptake in the Tanzanian population, albeit to varying degrees across age groups. Our study provides valuable insights for the planning and evaluation of similar social media communication campaigns aiming to bolster vaccination efforts.

Despite the overall benefits of immunization, vaccine hesitancy has been a growing trend and has been associated with the resurgence of vaccine-preventable diseases. The aim of this study was to assess vaccine confidence and hesitancy in Brazil, as part of a wider project to map vaccine confidence globally. One thousand subjects were interviewed, either online or face-to-face, based on a general questionnaire regarding perceptions on vaccines and vaccination. Further exploratory questions were used with the subset of respondents who were parents of children aged under 5. Such questions extracted information regarding vaccination behavior, opinions on vaccination and government health services, and vaccine hesitancy. Reasons for hesitancy were classified as relating to confidence, convenience and/or complacency, and the population was also analyzed socio-demographically. The results showed that overall confidence in immunization was higher than confidence in family planning services, community health workers and emergency services. Seventy-six people reported hesitancy to vaccinate. The commonest reasons for hesitancy were issues with confidence (41.4%), efficacy/safety of the vaccine (25.5%) and concerns about adverse events (23.6%). The sociodemographic analysis revealed that vaccine hesitancy was associated with marital status, level of education and income. Despite overall vaccine confidence being high, a clear trend toward lower levels of confidence was associated with higher levels of hesitancy, which warrants on-going monitoring, due to the dynamic and changing nature of vaccine hesitancy.

Vaccine hesitancy is listed as one of the top 10 global health threats by the WHO. Existing studies investigating the relationship between vaccine hesitancy and social media have found that misinformation and vaccine concerns on social media can cause significant declines in vaccine coverage rates. The objective of this study was to provide insight into the dynamics of vaccine messages on Twitter in Scandinavia (Denmark, Norway, Sweden), by analyzing tweets in local languages during 2019. A validated measure, the 5C scale, was used to map relevant predictors of vaccination behavior, capturing the factors confidence (in vaccines and the system that delivers them), complacency (not perceiving diseases as high risk), constraints (structural and psychological barriers), calculation (engagement in extensive information searching) and collective responsibility (willingness to protect others). A total of 1794 tweets met the inclusion criteria (DK: 48%, NO: 15%, SE: 37%), predominantly tweeted by private users (86%). The HPV vaccine was mentioned in 81% of tweets. Tweets were classified as expressing confidence (61%), complacency (18%), constraints (15%), calculation (15%), and collective responsibility (4%). Confidence in vaccines and the system that delivers them was expressed in 57%. A lack of confidence was expressed in 4% of all tweets, in combination with calculation in 39%. Analyzing public sentiment toward vaccination on Twitter is a useful tool to leverage for better understanding of the dynamics behind vaccine hesitancy. This analysis could provide actionable information for healthcare professionals and public health authorities to mitigate online misinformation and public vaccine concerns.

The COVID-19 pandemic is the most severe public health challenge the world has encountered. Although necessary precautions laid by the government are being followed to control the spread of the disease, vaccination is the only long-term answer to such a global issue. The COVID-19 vaccines have been rapidly developed and approved for emergency use. However, many people were hesitant to vaccinate against COVID-19 which reduced the success rate of vaccination programs. Through this research, we aim to study the reasons contributing to vaccine hesitancy and their probability of occurrence amongst the Indian population. A survey focusing on vaccine hesitancy and side effects of the COVID-19 vaccine was conducted and the data obtained were analyzed to understand the reasons behind vaccine hesitancy and the impact of side effects on the vaccination drive. The hesitation of people towards getting vaccinated revolves around a variety of aspects including, brand name, lack of confidence in vaccines and vaccination drive, conspiracy theories, educational and socio-economic status, underlying health issues, etc. Of notice, concern about side effects, and possible long-term side effects were the most important determinants. The severity of the short-term effects was found to be very low, implying that vaccination is completely safe and that people should get vaccinated against this virus as soon as possible and should not worry about side effects that are milder and shortlived. However, the real scenario of long-term side effects cannot be determined for now.

Teachers are an important occupational group to consider when addressing vaccine confidence and uptake for school-aged children due to their proximate role within school-based immunization programs. The objectives of this study were to characterize and identify sociodemographic factors associated with vaccine confidence and describe teachers' knowledge of and perceived role in the school-based immunization program, with the aim of informing public health policy and identifying opportunities for supporting teachers in their role in school-based immunization programs. A cross-sectional survey of elementary and secondary public-school teachers in British Columbia was completed from August to November 2020. Respondents provided sociodemographic information, as well as past vaccination experience, vaccine knowledge, and perceived role in the school-based immunization program. Vaccine confidence was measured using the Vaccine Hesitancy Scale (VHS). Characteristics associated with the VHS sub-scales 'lack of confidence in vaccines' and 'perceived risk of vaccines', were explored using ANOVA. Descriptive analysis was completed for teachers' perceived role in the immunization program. 5,095 surveys were included in this analysis. Overall vaccine confidence was high, with vaccine hesitancy being related to the perceived risk of vaccines rather than a lack of confidence in the effectiveness of vaccines. ANOVA found significant differences for both VHS-sub-scales based on sociodemographic factors, however, the strength of the association was generally small. High general vaccine knowledge and never having delayed or refused a vaccine in the past were associated with higher vaccine confidence. Overall, teachers reported a lack of clarity in their role within the school-based immunization program. This large population-based observational study of teachers highlights a number of key engagement opportunities between public health and the education sector. Using a validated scale, we found that overall, teachers are highly accepting of vaccines, and well situated as potential partners with public health to address vaccine hesitancy.

Understanding vaccine hesitancy, considering the target region and phase, is an urgent issue to quell the coronavirus disease (COVID-19) pandemic. This study aimed to monitor COVID-19 vaccine hesitancy in the Japanese population during the three phases of vaccine approval and introduction, and evaluate the association of vaccine hesitancy with vaccine confidence and literacy. We conducted web-based cross-sectional surveys during the three phases of COVID-19 vaccine introduction: January 2021, before approval; June, start of vaccination of the elderly; and September, when about 70% of the target population was vaccinated with at least one dose. There were 7210 participants, aged 20–80 years. We evaluated the association of vaccine hesitancy with vaccine confidence and literacy in the three phases using multivariate logistic regression analysis. The proportion of hesitancy in January, June, and September was 17.5%, 65.3%, and 19.4%, respectively. In any phase, lower vaccine confidence and literacy showed a higher adjusted odds ratio (AOR) of vaccine hesitancy in most items (AOR > 1, p < 0.001). Vaccine hesitancy in June had a different trend in perception of COVID-19 compared to that in the January and September surveys. The findings suggested that hesitancy increases transiently during vaccination introduction phases, and changes as the vaccination program progressed or waves of epidemic. Careful risk communication to increase vaccine confidence and literacy is essential to reduce vaccine hesitancy, especially in the introduction phase.

African immigrants in the U.S. may face elevated mpox exposure risks because they are more likely to travel to endemic regions where they maintain strong social and familial ties, while also encountering sociocultural barriers to vaccination. The ways in which mpox stigma and knowledge influence vaccine willingness, particularly through modifiable psychological pathways, remain unclear. To test whether mpox stigma and mpox knowledge are associated with willingness to receive an mpox vaccine via two mediators: vaccine confidence and vaccine hesitancy. We conducted a cross-sectional, web-based survey of African immigrants living in the U.S. (December 2024-July 2025; N = 139). We employed measures of mpox stigma, knowledge, vaccine confidence, vaccine hesitancy, and willingness to get vaccinated for mpox. Mediation analyses were performed, with 5,000 bootstrap resamples and 95% percentile confidence intervals (CI). Neither mpox stigma nor knowledge showed a significant association with willingness (p>.05). The indirect effect of mpox stigma on willingness through both confidence (B = - 0.21, CI [- 0.37, - 0.06]) and hesitancy (B = - 0.17, CI [- 0.32, - 0.01]) was significant. Specifically, higher mpox stigma was associated with lower vaccine confidence (B = - 0.24, p<.001) and greater vaccine hesitancy (B=0.18, p=.017), which in turn predicted willingness (confidence to willingness: B=0.89, p<.001; hesitancy to willingness: B = - 0.92, p<.001). Similarly, the indirect effect of mpox knowledge on willingness was significant through both confidence (B=0.05, CI [0.02, 0.08]) and hesitancy (B=0.03, CI[0.01, 0.05]), such that greater mpox knowledge was associated with higher confidence (B=0.05, p<.001) and reduced hesitancy (B = - 0.03, p=.008), which subsequently predicted willingness. Mpox vaccine willingness among African immigrants in the U.S. operates through vaccine confidence and hesitancy. Interventions that reduce stigma and build confidence with culturally responsive strategies may meaningfully improve uptake.

Declared as one of the ten most pressing threats to global health in 2019, the complexity around vaccine acceptance and hesitancy has once again gained great momentum following the COVID-19 pandemic. Lack of vaccine acceptance may endanger the mission of improving vaccine uptake globally to tackle pandemics, reduce morbidity and mortality of preventable diseases and to prevent antibiotic resistance worldwide. Countries of the global south, including South Asian Association for Regional Cooperation (SAARC) countries are especially affected by the dangers of low vaccination uptake and continue to show decreases in coverage in recent years. This paper examines factors contributing to vaccine hesitancy in south Asia and the extent to which they are context and disease specific, guided by a modified version of the WHO SAGE 5 C model by Razai et al. Three databases were searched for peer-reviewed articles by using a comprehensive search strategy. Results from 44 quantitative, qualitative and mixed-method studies were included in the systematic review and appraised for quality, thematically analyzed and mapped onto the 5 C model. findings from India, Pakistan, Bangladesh, Nepal and Afghanistan showed vaccine hesitancy to be context and vaccine-specific within different settings of the countries. The main factors contributing to vaccine hesitancy can be identified as narrow confidence in vaccines, miscommunication, and lack of knowledge embedded into overarching constraints and contexts. To tackle vaccine hesitancy in SAARC countries, interventions need to be co-created by communities and mutual trust needs to be ensured, for instance through increased equity in knowledge distribution.

Recent advances in artificial intelligence (AI) coincide with decreases in confidence in vaccines. This review examines studies that analyze and mitigate vaccine skepticism by implementing artificial intelligence strategies in various ways. Studies have explored public attitudes towards vaccines using AI to analyze language in social media postings and interactions, scrutinize AI responses to vaccine-related queries, and attempt to use AI to directly influence vaccine hesitancy. Findings show that AI can be effective in addressing vaccine hesitancy in various ways, including, but not limited to, directly interacting with vaccine-hesitant groups, identifying reasons for vaccine hesitancy, and predicting vaccine hesitancy among specific populations. AI will undoubtedly continue to evolve and improve over the coming years. Continued advances and new applications can help mitigate unwarranted vaccine hesitancy in a variety of ways, such as educating people with messaging tailored to end users or using AI to identify the specific concerns of vaccine-hesitant individuals and groups. It will require an integrative approach to a complex issue - vaccine hesitancy is not a monolith; there is a range of degrees of vaccine hesitancy, and various factors go into a person's vaccine knowledge and beliefs.

Vaccine hesitancy is an important public health issue referring to concerns about the safety and efficacy of vaccination. Within a framework, this study aimed to assess the cultural adaptation, validity, and reliability of the Greek version of the adult Vaccine Hesitancy Scale (aVHS) as well as to identify the determinants of vaccine hesitancy among a large regional population in central Greece. A cross-sectional study was conducted enrolling 300 adults who had received primary healthcare services in the Health Centers and Local Health Units of the Magnesia Region from October to December 2022. The aVHS and the Life Orientation Test-Revised (LOT-R) were used to identify vaccine hesitancy and the dispositional level of optimism, respectively. For survey translation, the procedure of forward and backward translation was followed. Also, the aVHS was tested in a pilot study with a sample of 18 responders. Construct validity and internal consistency reliability were investigated via exploratory and confirmatory factor analysis and Cronbach's alpha coefficients, respectively. Simple and multiple linear regression analysis were used to determine predictors for vaccine hesitancy. Factor analyses indicated that the aVHS comprises two constructs ("lack of confidence" and "risk perception") explaining 68.9% of the total variance. The Cronbach's alpha of the total scale was 0.884, indicating its high internal consistency. Participants who lived in rural areas, had a lower annual income, and reported a lower level of optimism showed a higher lack of confidence in vaccination. On the other hand, people aged above 45 years old who had graduated from high school or elementary school and were unemployed showed greater aversion to the risks of side effects. Finally, certain socio-demographic characteristics were associated with vaccine hesitancy. Our data suggest that the aVHS is a valid and reliable instrument for measuring vaccine-related attitudes and perceptions in Greek society, providing meaningful insight into designing vaccination-related preventive interventions in the community.

A cultural evolutionary model of the interaction between parental beliefs and behaviors, with applications to vaccine hesitancy