In today’s society, where decisions about vaccination and doubts about the safety and effectiveness of vaccines pose challenges not just for public health but for all aspects of society, it’s crucial to explore vaccine hesitancy from a sociological perspective. Historically, vaccines have contributed to eradicating smallpox, nearly eliminating polio, and reducing the incidence of diseases such as tetanus or measles. Nevertheless, despite the well-known success of vaccines, the recent pandemic highlighted a persistent societal and healthcare challenge – vaccine hesitancy – which has existed since the earliest days of vaccination. In this dissertation, vaccine hesitancy is broadly defined as general uncertainty about vaccines, although common definition proposed by World Health Organization group sees vaccine hesitancy as a delay in making a vaccination decision, reflecting a spectrum between outright refusal and partial acceptance. In many public health campaigns, vaccine hesitancy is often viewed as consequence of insufficient information (Goldenberg, 2016). This perspective presupposes that people are “uninformed” and that simply providing them with knowledge, like wielding a magic wand, will eliminate all doubts and negative attitudes toward vaccines. It also appears, at least implicitly, in arguments that attribute negative attitudes toward science in general, or toward vaccination in particular, to so-called “unthinking” laypersons. The recent pandemic made it clear that many countries struggled to reach their vaccination goals, despite public health campaigns and efforts by scientists to inform people about vaccine’s safety. This reveals that concerns about vaccines go beyond knowing evidence-based facts and point to a deeper, more complex relationship between science and society. In addition to “uninformed citizens” and anti-vaccination narratives, the pandemic was also characterized by excessive dissemination of both information and misinformation in traditional and contemporary media, as well as the lack of trust in broad spectre of institutions. This is especially relevant given that conspiratorial anti-vaccine narratives are particularly appealing to those who, in light of the aforementioned context, are disinclined to trust information coming from authorities such as scientists, healthcare professionals or political representatives. By defining the issue of vaccine hesitancy solely as a problem of insufficient information, this broader context can be overlooked. Consequently, what appears to be a purely medical topic needs to be situated within a sociological framework that recognizes vaccine hesitancy as a part of the broader relationship between science and society. Such a perspective underscores the importance of additional variables in shaping negative attitudes toward science in general, and more specifically, toward vaccine-related issues. With this in mind, dissertation titled Testing the Deficit Model and the Contextual Model of Vaccine Hesitancy, focuses on understanding the relationship between vaccine hesitancy and various factors such as scientific and health literacy, belief in vaccine conspiracy theories, distrust in the healthcare system, religiosity, and political identification. The research is framed using two models of public understanding of science: the deficit model, which attributes hesitancy to a lack of knowledge or scientific literacy, and the contextual model, which emphasizes the role of social, cultural and other aspects relevant for vaccine hesitancy. The deficit model helps explain how scientific literacy shapes “lay” attitudes toward science, assuming that a better-informed public will be more positively disposed toward scientific findings (Miller, 1983,1998). This model primarily focuses on shortfall in “textbook” knowledge, which purportedly leads to scepticism (Sturgis & Allum, 2004). In the deficit model, scientific literacy bridges scientists and the public by emphasizing reliable information, critical thought, factual knowledge and education. Critics note that ambiguous definitions complicate measuring scientific literacy universally. Moreover, Goldenberg (2016) points out that misunderstanding science does not alone explain reluctance or refusal of vaccines; rejection may reflect deeper resistance to the values underlying scientific consensus. Contrary to the deficit model, the so-called contextual model suggests that knowledge is accumulated and applied within specific sociocultural contexts. This perspective emerged as a critique of the traditional positivist view of how scientific and technological information shapes public understanding of science in general, and vaccine hesitancy in specific. It challenges the central assumptions of the deficit model and underscores the plurality of knowledge that informs attitudes toward science and technology in general (Sturgis & Allum, 2004). Some scholars (Brossard and Lewenstein, 2009) explain that people are not “empty containers” but instead filter scientific information through their life experiences, thereby connecting individual and social factors to the issue of vaccine hesitancy and public understanding of science in general. In this light, some authors highlight trust in scientific expertise as crucial for contextualizing scientific knowledge (Rosman & Grösser, 2024). The emphasis lies on the applicability and social embeddedness of knowledge, where a person’s motivation to absorb new scientific insights is shaped by perceived benefits and relevance of science within their social milieu (Eisendel, 2000; Felt, 1999; Wynne, 1992). In this dissertation, studies have been highlighted which indicate that the link between scientific knowledge and attitudes toward science is not straightforwardly linear, but rather contextualized by various domains of knowledge and sociocultural variables. Based on previous research and empirical evidence, this dissertation sets out several key objectives. First, it aims to explain vaccine hesitancy by testing two models of public understanding of science, focusing on the role of scientific and health literacy, conspiracy beliefs, distrust in healthcare, religiosity, and political orientation. Second, it explores how vaccine hesitancy differs between well-established childhood immunizations and newer COVID-19 vaccines, recognizing that the pandemic has introduced additional factors—such as adherence to public health measures and information overload—for consideration. Finally, from a sociological perspective, the dissertation seeks to generate practical insights for public health interventions and campaigns designed to reduce vaccine hesitancy. To achieve the objectives of this dissertation, a quantitative data collection method was employed. The study population included citizens of the Republic of Croatia aged 18 to 65, stratified by region, settlement size, gender, and age (N=1306). Specifically, an online quantitative survey was conducted using a probabilistic sample stratified by age, gender, settlement size, and region. The Ipsos agency was commissioned to carry out the data gathering, which took place through the CAWI (Computer-Assisted Web Interviewing) method using Ipsos’s online panel. This decision was largely influenced by the pandemic context (2022) which includes a series of lockdowns and a rise in COVID-19 cases, that led to the conclusion that conducting an online panel survey would be the safest and most efficient way to protect public health and maintain research efficacy. The questionnaire, constructed from the measurement scales discussed in this dissertation, required approximately 20 minutes to complete and omitted open-ended questions to reduce the time burden on participants and facilitate straightforward quantitative coding. This study employed several measurement scales to capture various dimensions related to vaccine hesitancy, scientific and health literacy, vaccine conspiracy beliefs, distrust in healthcare systems, religiosity, and political identification. Vaccine hesitancy toward childhood vaccines was measured using the WHO’s Vaccine Hesitancy Scale (VHS), consisting of ten items assessing attitudes about vaccine importance, efficacy, safety, and the credibility of vaccine-related information. Hesitancy toward COVID-19 vaccines, on the other hand, was assessed through the OC19-VHS scale, which was specifically developed to gauge public attitudes relating to COVID-19 vaccine safety and effectiveness. To evaluate scientific literacy, the well-known Oxford Scientific Literacy Scale was employed. Health literacy was measured using HLS-EU-Q6, a concise, six-item scale that focuses on people’s ability to interpret health information and follow medical instructions. Beyond these measures, the study also incorporated a scale designed to assess belief in vaccinerelated conspiracy theories. Distrust in the healthcare system was evaluated with the Revised Health Care System Distrust Scale (RHCSDS), which distinguishes between trust in the system’s competence and reliability, and distrust in its moral and ethical values. Finally, two additional variables, religiosity and political identification, were captured through single-item measures. Religiosity was gauged through a 10-point scale where higher numbers represent a stronger sense of religious identity. Political identification was also measured through a 10- point scale extending from left-leaning views to right-leaning ones. A set of few hypotheses has been formulated, positing that greater levels of literacy reduce vaccine hesitancy, whereas stronger beliefs in conspiracy theories, higher religiosity, elevated distrust, and right-wing political orientations are likely to increase it. In parallel, a moderating effect of distrust and conspiracy beliefs is anticipated, implying that the beneficial role of literacy in mitigating vaccine hesitancy would weaken among individuals exhibiting moderate or high levels of distrust or belief in vaccine-related conspiracy theories. The analytical approach in this dissertation is structured around Structural Equation Modelling (SEM), applied to investigate the complex interplay of factors influencing vaccine hesitancy. The SEM approach was chosen due to its capacity to estimate multiple interrelated paths simultaneously, allowing for a more comprehensive examination of direct, indirect, and moderated effects. A critical aspect of the analytical procedure involves parcelling, a technique used to optimize the measurement model by reducing the number of indicators per latent variable. This method was employed to create composite indicators for scientific literacy, health literacy, and institutional trust, thereby enhancing the stability of parameter estimates and mitigating issues related to measurement error. The parcelling strategy followed the item-to-construct balance approach, ensuring that each parcel adequately represented the theoretical construct without distorting its underlying structure. Moderation analysis played a central role in testing the hypothesis that healthcare distrust and conspiracy beliefs weaken the expected negative relationship between literacy and vaccine hesitancy. This was conducted using multiplicative interaction terms, wherein moderator variables (institutional distrust and conspiracy beliefs) were centered before interaction terms were computed to prevent multicollinearity. The model evaluation relied on multiple goodnessof-fit indices, such as the Comparative Fit Index (CFI), Tucker-Lewis Index (TLI), Root Mean Square Error of Approximation (RMSEA), and the chi-square test of model fit. This approach allowed for a more refined understanding of how structural skepticism and ideological resistance shape vaccine attitudes beyond simple knowledge deficits. The findings suggest that higher levels of scientific and health literacy are only weakly associated with lower vaccine hesitancy. Moreover, when other factors are considered, it appears that they have a much stronger association with vaccine hesitancy. Additionally, the dissertation examines the specific context of hesitancy regarding the groups that appear to have higher levels of hesitancy, while paying particular attention to the specific challenges related to COVID-19 vaccines. The study underscores that addressing vaccine hesitancy and rebuilding public trust in experts is not simply a matter of introducing scientific facts about vaccines. Rather, it requires and understanding of the broader social, cultural and individual factors that shape public attitudes toward vaccines and public understanding of science. The dissertation calls for interdisciplinary collaboration to address the current research gaps and provide deeper insights into the complexities of vaccine hesitancy and public understanding of science.