Social nudges for vaccination: How communicating herd behaviour influences vaccination intentions

Should Public Communication of Vaccination Rates Assume Rationality, Normativity or Reasonableness? Insights from Three Preregistered Experiments

The proportion of the population who are vaccinated against an infectious disease is significant - not only because vaccination keeps the virus from spreading, but also because learning about how many members of one's community have decided to get vaccinated has been shown to affect individual vaccination intention. In three preregistered online experiments featuring country-level vaccination rates against a hypothetical disease, we tested two theoretical approaches which offer contrasting predictions on how public health messaging should leverage vaccination rates. If selfish rationality is assumed, a high uptake would tempt people to free-ride on herd immunity (so low uptake should be emphasized); conversely, if vaccination rates exert a descriptive normative influence, a high uptake would signal that vaccination is the best choice, and vice versa (so high uptake should be emphasized). In the pilot (N = 75) and Experiment 1 (N = 174), communicating a high (90%) vaccination rate (vs. 10% vs. no rate) increased vaccination intentions, with no detectable effect of a low vaccination rate. In Experiment 2 (N = 217), decisions to get vaccinated were frequently justified based on reasons involving self-protection, but also the protection of others and the collective, irrespective of the vaccination rate level (20% vs. 80%); participants, on the other hand, rarely endorsed any of the tested reasons for non-vaccination, including free-riding; furthermore, descriptive norms were perceived as more relevant for vaccination than non-vaccination decisions. Experiment 3 (N = 1060) tested the effectiveness of different messages when the majority have been vaccinated (60%) but the coverage is still not optimal. Alongside a weak descriptive norm, the self-benefit message worked better than other- and collective-benefit messages. We argue that public health messaging should incorporate both theoretical approaches, closer to the notion of reasonableness (rather than pure rationality or normativity), which is context-sensitive and pragmatic.

Compliance with social norms in the face of risks: Delineating the roles of uncertainty about risk perceptions versus risk perceptions

Social norms are often considered as behavioral guidelines to mitigate health and environmental risks. However, our understanding of the magnitude of their impact on risk-mitigating behaviors and how perceptions of risks affect the magnitude remains limited. Given the increasing importance of understanding factors influencing behavioral responses to health and environmental risks, this research examines whether the relationship between social norms and behavioral intention to mitigate health and environmental risks is a function of (1) risk perceptions and (2) uncertainty about risk perceptions. A cross-sectional survey involving a national sample (N = 803) across three health and environmental risks (i.e., infectious diseases, climate change, and water shortage) is conducted. The results reveal a three-way interaction between descriptive norms, uncertainty about susceptibility, and uncertainty about severity on behavioral intention to mitigate the risk. Individuals exhibit the strongest intention to engage in risk-mitigating behaviors when they perceive prevailing social norms and are uncertain about their susceptibility to the risk and the severity of the risk. Moreover, injunctive norms interact with uncertainty about susceptibility to influence behavioral intention, such that the more uncertain individuals feel about their vulnerability to a risk, the stronger the impact of injunctive norms is on behavioral intention. Neither descriptive nor injunctive norms interact with perceived risks to influence behavioral intention. This study contributes valuable insights into the interplay between social norms, uncertainty about perceived risk, and behavioral intention, and offers valuable theoretical and practical implications.

Vaccine hesitancy: a structured review from a behavioral perspective (2015-2022)

Vaccine hesitancy, a complex behavioral phenomenon, poses a significant global health threat and has gained renewed attention amidst the COVID-19 pandemic. This paper scrutinized peer-reviewed literature on vaccine hesitancy published from 2015 to 2022, with a specific focus on behavioral perspectives, utilizing a Theories-Constructs-Variables-Contexts-Methods (TCVCM) framework. The study highlighted prominent theoretical approaches, abstract concepts, research variables, global contexts and academic techniques employed across a selected sample of 138 studies. The result is a consolidated overview of research and schematization of the factors influencing vaccine hesitancy and vaccination behaviors. These include individual-level, contextual, vaccine-specific, organizational, and public-policy-related dynamics. The findings corroborated the complexity of vaccine hesitancy and emphasized the difficulties of pursuing vaccine advocacy. The analysis also identified several directions for future research, and the need to conduct more contextual studies in low- and middle-income nations to bring out the cross-cultural nuances of vaccine hesitancy.

Categorising interventions to enhance vaccine uptake or reduce vaccine hesitancy in the United Kingdom: A systematic review and meta-analysis

BACKGROUND

Vaccination is one of the most important public health interventions to combat infectious disease. However, vaccine hesitancy prevents us reaching the global target of vaccine uptake (e.g., 75 % of influenza vaccination in at-risk groups). This review summarises all interventions designed to reduce vaccine hesitancy and increase vaccine uptake for all types of vaccines offered to adults (≥18 years) since 2000, in the United Kingdom (UK).

METHODS

PubMed, Cochrane Reviews, CINAHL EBSCO, and Scopus were searched (September 19, 2023). The PRISMA Checklist 2020 was used for quality checking. Data from randomised-controlled trials (RCTs) were analysed with a meta-analysis and narrative analysis. In all included studies, a narrative synthesis was undertaken to summarise, evaluate and characterisethe reported behaviour change interventions into four categories: organisational-level, public demand, provider-level, and multidimensional interventions. Findings are evaluated based on the MINDSPACE framework to understand the possible psychological mechanisms underpinning the interventions.

FINDINGS

A total of 9,842 articles were identified, 50 met the inclusion criteria. Interventions aimed to boost vaccine uptake or reduce hesitancy of influenza (50 %), COVID-19 (32 %), hepatitis B (6 %), and other vaccines. A meta-analysis was conducted for nine RCTs evaluating various interventions impact on vaccine uptake. The pooled effect was statistically significant (OR with 95 % CI = 1.23 [1.07 to 1.41]). Providing certain and understandableinformation and using a reminder system with personal messages or letters were the most frequently documented and effective interventions to enhance public demand (enhance information salience). Organisational level interventions intended to make vaccinations more accessible (e.g., providing vaccination at alternative places or times). Provider-oriented interventions encouraged healthcare workers to focus on reducing vaccine hesitancy or enhancing vaccine uptake.

INTERPRETATION

Among the main MINDSPACE techniques, enhancing the salience of vaccine information and priming vaccination by improving access were identified as the most applied and effective interventions in the UK.

Negativity in online news coverage of vaccination rates in Serbia: a content analysis

OBJECTIVE

This content analysis study explored how online news media communicates and frames vaccination rates and herd immunity (the effect where enough people are immune, the virus is contained).

METHODS

We analyzed 160 vaccination-related news stories by nine highest-trafficked news websites in Serbia, published July-December 2017, around the start of the measles outbreak. We coded both the news story as a whole and every vaccination-rate mention (N = 339).

RESULTS

News stories framed current vaccination rates and changes in them in a predominantly negative way (175/241 and 67/98 mentions, respectively) (e.g., "only 50% vaccinated", "fewer parents vaccinating their children"), especially when referring to the measles vaccine (202/262 mentions). A total of 23/86 of news stories mentioning vaccination rates did not provide any numerical values. Reference groups for vaccination rates were rarely specified. Out of the 32 news stories mentioning herd immunity, 11 explained the effect.

CONCLUSIONS

Even routine communication of vaccination rates can be biased through negative frames and imprecise descriptions. Lamenting low immunization rates could activate a negative descriptive social norm ("many people are not getting vaccinated"), which may be especially ill-advised in the absence of an explanation of the social benefit of achieving herd immunity through vaccination.

Moral characteristics predicting COVID-19 vaccination

OBJECTIVE

The current study aims to assess, for the first time, whether vaccination is predicted by different behavioral and cognitive aspects of moral decision-making.

BACKGROUND

Studies linking moral factors to vaccination have largely examined whether vaccination decisions can be explained by individual differences in the endorsement of various principles and norms central to deontology-based arguments in vaccination ethics. However, these studies have overlooked whether individuals prioritize norms over other considerations when making decisions, such as maximizing consequences (utilitarianism).

METHOD

In a sample of 1492 participants, the current study assessed whether vaccination is explained by individual differences in three aspects of moral decision-making (consequence sensitivity, norm sensitivity, and action tendency), while also considering ethics position (idealism, relativism) and moral identity.

RESULTS

Supportive vaccination (vaccine uptake accompanied by a positive attitude toward vaccines) was associated with utilitarianism (increased consequence sensitivity) and increased tolerance to risks and harm toward others. Meanwhile, although those in the non-vaccinated group was associated with higher harm sensitivities, they neither supported nor received the COVID vaccines (when vaccines prevent harm from infection).

CONCLUSION

Pro-vaccination messages may be made more effective by addressing perceptions of harms associated with vaccines and infections, respectively.

Political network composition predicts vaccination attitudes

Political polarization is growing rapidly in the United States and has been linked to politicized public health issues including vaccination. Political homogeneity among one's interpersonal relationships may predict polarization levels and partisan bias. In this study, we analyzed if political network structure predicted partisan beliefs about the COVID-19 vaccine, beliefs about vaccines in general, and COVID-19 vaccine uptake. Personal networks were measured by whom the respondent discussed "important matters" with to obtain a list of individuals who are close to the respondent. The number of associates listed who share the political identity or vaccine status with the respondent was calculated as a measure of homogeneity. We find that having more Republicans and unvaccinated individuals in one's network predicted lower vaccine confidence whereas having more Democrats and vaccinated individuals in one's network predicted higher vaccine confidence. Exploratory network analyses revealed that non-kin others are especially impactful on vaccine attitudes when those network connections are also Republican and unvaccinated.

Knowledge, Attitudes and Practices toward Dengue Fever, Vector Control, and Vaccine Acceptance Among the General Population in Countries from Latin America and Asia Pacific: A Cross-Sectional Study (GEMKAP)

Dengue represents a major public health concern. With effective vaccines in development, it is important to identify motivational factors to maximize dengue vaccine uptake. A cross-sectional, quantitative, electronic survey was administered to a nationally representative adult population (n = 3800) in Argentina, Brazil, Colombia, Mexico, Indonesia, Malaysia, and Singapore. Willingness to vaccinate against dengue, and Knowledge, Attitudes, and Practices (KAP) toward dengue, vector control, prevention, and vaccination were determined. The Capability, Opportunity, Motivation for Behavior change (COM-B) framework was used to identify factors correlated with dengue vaccine(s) uptake. KAP scores (standardized, 0–100% scale) resulted in a low global score for Knowledge (48%) and Practice (44%), and a moderate score for Attitude (66%); scores were comparable across countries. Of all respondents, 53% had a high willingness (Score: 8–10/10) to vaccinate against dengue, which was higher (59%) in Latin America (Argentina, Brazil, Colombia, Mexico) than in Asia Pacific (40%) (Indonesia, Malaysia, Singapore). Key factors significantly (p < 0.05) associated with increased willingness to vaccinate included accessibility to the public (subsidies and incentives) and trust in the healthcare system and government. A common approach to dengue prevention across endemic countries––with some country-specific customization, including education, vaccination, and vector control (multi-pronged)––may reduce dengue burden and improve outcomes.

Do social media campaigns foster vaccination adherence? A systematic review of prior intervention-based campaigns on social media

The COVID-19 pandemic has demonstrated the importance of large-scale campaigns to facilitate vaccination adherence. Social media presents unique opportunities to reach broader audiences and reduces the costs of conducting national or global campaigns aimed at achieving herd immunity. Nonetheless, few studies have reviewed the effectiveness of prior social media campaigns for vaccination adherence, and several prior studies have shown that social media campaigns do not increase uptake rates. Hence, our objective is to conduct a systematic review to examine the effectiveness of social media campaigns and to identify the reasons for the mixed results of prior studies. Our methodology began with a search of seven databases, which resulted in the identification of 92 interventions conducted over digital media. Out of these 92 studies, only 15 adopted social media campaigns for immunization. We analyzed these 15 studies, along with a coding scheme we developed based on reviews of both health interventions and social media campaigns. Multiple coders, who were knowledgeable about social media campaigns and healthcare, analyzed the 15 cases and obtained an acceptable level of inter-coder reliability (> .80). The results from our systematic review show that only a few social media campaigns have succeeded in enhancing vaccination adherence. In addition, few campaigns have utilized known critical success factors of social media to induce vaccination adherence. Based on these findings, we discuss a set of research questions that informatics scholars should consider when identifying opportunities for using social media to resolve one of the most resilient challenges in public health. Finally, we conclude by discussing how the insights drawn from our systematic reviews contribute to advancing theories, such as social influence and the health belief model, into the realm of social media-based health interventions.

How growers make decisions impacts plant disease control

While the spread of plant disease depends strongly on biological factors driving transmission, it also has a human dimension. Disease control depends on decisions made by individual growers, who are in turn influenced by a broad range of factors. Despite this, human behaviour has rarely been included in plant epidemic models. Considering Cassava Brown Streak Disease, we model how the perceived increase in profit due to disease management influences participation in clean seed systems (CSS). Our models are rooted in game theory, with growers making strategic decisions based on the expected profitability of different control strategies. We find that both the information used by growers to assess profitability and the perception of economic and epidemiological parameters influence long-term participation in the CSS. Over-estimation of infection risk leads to lower participation in the CSS, as growers perceive that paying for the CSS will be futile. Additionally, even though good disease management can be achieved through the implementation of CSS, and a scenario where all controllers use the CSS is achievable when growers base their decision on the average of their entire strategy, CBSD is rarely eliminated from the system. These results are robust to stochastic and spatial effects. Our work highlights the importance of including human behaviour in plant disease models, but also the significance of how that behaviour is included.

Vaccine Hesitancy Under the Magnifying Glass: A Systematic Review of the Uses and Misuses of an Increasingly Popular Construct

Resistance to vaccines has hindered attempts to contain and prevent outbreaks of infectious diseases for centuries. More recently, however, the term "vaccine hesitancy" has been used to describe not necessarily outright resistance but also a delay in acceptance or uncertainty regarding vaccines. Given concerns about hesitancy and its impact on vaccine uptake rates, researchers increasingly shifted the focus from resistance to vaccines toward vaccine hesitancy. Acknowledging the urgency to accurately assess the phenomenon, it is critical to understand the state of the literature, focusing on issues of conceptualization and operationalization. To carry out this systematic review, we collected and analyzed all published empirical articles from 2000 to 2021 that explicitly included quantitative self-report measures of vaccine hesitancy (k = 86). Using a mixed-method approach, the review demonstrates and quantifies crucial inconsistencies in the measurement of the construct, lack of clarity in regard to the determination of who should or should not be defined as hesitant, and overreliance on unrepresentative samples. Crucially, our analysis points to a potential systematic bias toward exaggerating the level of hesitancy in the population. Modeling a vaccine hesitancy co-citation network, the analysis also points to the existence of insular academic silos that make it harder to achieve a unified measurement tool. Theoretical and practical implications for academics, practitioners, and policymakers are discussed.