5C Scale of Psychological Antecedents of Vaccination

Abstract

The 5C Scale of Psychological Antecedents of Vaccination is an advanced, theoretically grounded psychometric instrument designed to assess the cognitive, affective, and behavioral drivers of vaccination decisions. Developed to overcome the conceptual limitations of unidimensional vaccine hesitancy measures—which frequently conflated structural access barriers with active skepticism—the instrument operationalizes five distinct psychological antecedents: Confidence, Complacency, Constraints, Calculation, and Collective Responsibility. By expanding upon the World Health Organization Strategic Advisory Group of Experts (WHO SAGE) 3C model, the 5C scale offers a fine-grained behavioral diagnosis across both individual decision-making processes and prosocial orientations toward community protection. Available in both a comprehensive 15-item standard battery and an abbreviated 5-item screening format, the scale utilizes a multi-point metric to quantify latent attitudes toward immunization. Across multiple psychometric evaluations encompassing diverse cross-sectional and longitudinal cohorts of nearly 2,800 participants, the instrument demonstrates robust internal consistency (Cronbach’s α and McDonald’s ω values typically exceeding .70 across subscales), rigorous structural integrity through confirmatory factor analysis (CFA), strong convergent and discriminant validity against established health-belief metrics, and high predictive power regarding actual vaccine uptake. By elucidating specific psychological barriers, the scale empowers epidemiologists, behavioral scientists, and public health strategists to implement tailored, evidence-based communication frameworks and health policies.

Keywords

vaccine hesitancy, psychological antecedents, 5C model, immunization behavior, psychometrics, health psychology, confidence, complacency, structural constraints, calculation, collective responsibility

Authors

The 5C Scale of Psychological Antecedents of Vaccination was developed by a team of researchers in health psychology, behavioral economics, and communication science:

• Cornelia Betsch, PhD — Center for Empirical Research in Economics and Behavioral Sciences (CEREB) and Media and Communication Science, University of Erfurt, Germany. Email: [email protected].
• Philipp Schmid, PhD — Media and Communication Science, University of Erfurt, Germany.
• Dorothee Heinemeier, MSc — Media and Communication Science, University of Erfurt, Germany.
• Lars Korn, PhD — Media and Communication Science, University of Erfurt, Germany.
• Cindy Holtmann, MSc — Media and Communication Science, University of Erfurt, Germany.
• Robert Böhm, PhD — School of Business and Economics, RWTH Aachen University, Aachen, Germany.

Purpose

Immunization against infectious diseases represents one of the most cost-effective and transformative public health interventions in modern medicine. Nevertheless, the emergence of widespread vaccine hesitancy—defined as a delay in acceptance or outright refusal of vaccination despite the availability of vaccination services—has threatened the maintenance of herd immunity thresholds globally. Historically, public health surveillance systems operationalized vaccine attitudes primarily through dichotomous behavioral classifications (i.e., vaccinated versus unvaccinated) or unidimensional metrics centered narrowly on trust in vaccine safety. These approaches failed to capture the multifaceted cognitive architecture underlying immunization decisions. Individuals may remain unvaccinated due to physical, economic, or logistical barriers; alternatively, they may perceive negligible vulnerability to target pathogens, engage in protracted and biased risk-benefit assessments, or deliberately free-ride on the immunity of their peers.

To address this measurement gap, the 5C Scale was engineered to provide an empirically rigorous diagnostic tool capable of delineating the specific psychological antecedents governing vaccine uptake. Rather than applying a blanket diagnosis of “anti-vaccine sentiment,” the instrument enables researchers, clinicians, and epidemiologists to conduct granular profiling of target populations. The scale clarifies whether low coverage is driven by epistemological distrust, low threat perceptions, behavioral friction, obsessive information search, or a deficit in prosocial motivation.

In clinical environments, the 5C scale functions as a diagnostic screen that allows primary care providers to tailor risk communication to the specific cognitive profile of the patient. In public health administration, the scale serves as a surveillance metric for monitoring longitudinal shifts in population sentiment, diagnosing localized outbreaks of hesitancy, and evaluating the efficacy of targeted health policy interventions. By differentiating between operational barriers and intrinsic cognitive hesitations, the tool ensures that interventions deploy resources efficiently—such as deploying mobile clinics for structural constraints or targeted debunking campaigns for calculation-driven misinformation.

Psychological Construct

The 5C model conceptualizes vaccination behavior as the downstream outcome of five interrelated yet functionally distinct psychological constructs:

1. Confidence

Confidence denotes trust in the safety and efficacy of vaccines, the reliability and competence of the healthcare delivery system, and the integrity of regulatory bodies and policy-makers who sanction immunization schedules. High confidence reflects a psychological state in which vaccines are perceived as safe, effective, and administered in the public interest. Conversely, a lack of confidence involves profound skepticism, suspicion of corporate or political conflicts of interest, and anxiety regarding adverse events.

2. Complacency

Complacency captures a psychological state characterized by low perceived disease vulnerability and low perceived disease severity. When individuals assess vaccine-preventable infections as rare, benign, or manageable through personal lifestyle factors (e.g., natural immunity, physical fitness, or dietary habits), vaccination is deemed an unnecessary or redundant preventive measure. Complacent individuals do not actively harbor anti-medical hostility; rather, vaccination simply occupies a minimal priority within their subjective health-maintenance hierarchy.

3. Constraints

Constraints encompass the physical, structural, financial, and psychological barriers that impede access to vaccination services. Moving beyond passive notions of convenience, this construct directly assesses operational friction. Physical barriers include clinic accessibility, geographical proximity, transportation availability, and flexible clinic hours. Financial constraints encompass out-of-pocket costs and administrative complexities, while psychological constraints involve somatic stress, needle phobia, physician-related anxiety, and cognitive overload. Elevated constraints suppress uptake even when intrinsic motivation and confidence are high.

4. Calculation

Calculation reflects an individual’s engagement in extensive, deliberate, and effortful information search and cognitive evaluation of risks and benefits (consistent with System-2 dual-process cognition). Highly calculative individuals do not accept normative medical recommendations passively; instead, they weigh pathogen risks against potential vaccine side effects through exhaustive literature searches. In contemporary digital ecosystems saturated with pseudoscientific misinformation, heightened calculation often paradoxically increases hesitancy by exposing the decision-maker to alarmist narratives and unverified adverse event reports.

5. Collective Responsibility

Collective Responsibility operationalizes the prosocial and communal dimension of vaccination. It measures an individual’s willingness to undergo vaccination not merely for personal prophylaxis, but to protect vulnerable members of society through herd immunity (e.g., infants, immunocompromised individuals, and older adults). Conversely, low collective responsibility manifests as a willingness to “free-ride” on the population immunity provided by the compliance of others without contributing to communal protection.

Theoretical Framework

The 5C model synthesizes foundational paradigms across health psychology, behavioral economics, and cognitive decision theory. It directly evolves from the World Health Organization’s 3C model proposed by the SAGE Working Group, which posited that vaccine hesitancy is governed by Confidence, Complacency, and Convenience. While conceptually valuable, the 3C framework suffered from psychometric ambiguity, particularly regarding the “Convenience” dimension, which conflated objective healthcare access with subjective perceptions of effort.

To establish psychological rigor, the 5C model replaced “Convenience” with Constraints, grounding it in the Theory of Planned Behavior (TPB) developed by Icek Ajzen. In this synthesis, Constraints operationalize barriers to perceived behavioral control, reflecting both external structural determinants and internal self-efficacy limitations. The Complacency dimension directly integrates core tenets of the Health Belief Model (HBM), explicitly mapping onto perceived susceptibility and perceived severity of infectious threats.

The introduction of Calculation incorporates dual-process theories of cognition (e.g., Stanovich & West; Kahneman). When individuals transition from heuristic, trust-based default decisions (System 1) to explicit, deliberative utility calculation (System 2), they encounter epistemic vulnerabilities caused by confirmation bias and selective exposure. Finally, Collective Responsibility integrates insights from public goods game theory and social dilemma research. Because vaccination yields positive external benefits that shield third parties from transmission, decision-makers face a social dilemma: incur the private cost of injection or free-ride on the communal shield. By operationalizing prosocial motivation, the 5C model captures the altruistic utility that offsets perceived individual costs.

Validity

The validity of the 5C Scale has been rigorously confirmed through extensive construct, convergent, discriminant, and predictive psychometric investigations.

Content and Construct Validity

Initial item pools were generated through systematic reviews of vaccine hesitancy literature and expert panel adjudication. Each item was formulated to capture the theoretical core of its target antecedent while avoiding contamination with downstream behavioral intentions.

Convergent and Discriminant Validity

Across extensive validation cohorts totaling nearly 2,800 participants across multiple studies, the 5C subscales exhibited strong, theory-congruent associations with established psychometric inventories:

• Confidence: Demonstrated large positive correlations with general trust in the healthcare system (e.g., Multidimensional Trust in Health Care Systems Scale, r ≈ .65 to .72), positive attitudes toward conventional medicine, and robust negative correlations with generic conspiracy ideation (measured via the Conspiracy Mentality Questionnaire, r ≈ −.45 to −.55).
• Complacency: Inversely correlated with perceived disease vulnerability (r ≈ −.58), objective risk literacy (e.g., Berlin Numeracy Test), and fear of disease sequelae.
• Constraints: Strongly correlated with measures of everyday stress, perceived structural access difficulties, and needle fear, while showing negative associations with perceived self-efficacy.
• Calculation: Correlated significantly with preference for deliberation (PID-Deliberation scale, r ≈ .38), extensive health information-seeking behaviors, and analytical cognitive styles, operating orthogonally from confidence.
• Collective Responsibility: Correlated robustly with generalized empathy (e.g., Toronto Empathy Questionnaire, r ≈ .42), communal orientation, and prosocial value orientations in public goods economic paradigms.

Criterion and Predictive Validity

The predictive validity of the scale was established by modeling reported and verified vaccination behaviors against multiple infectious agents, including influenza, human papillomavirus (HPV), and routine adult boosters. Logistic regression models indicated that the 5C subscales accounted for significant unique variance in vaccination uptake, substantially outperforming traditional unidimensional hesitancy indicators. High Confidence and Collective Responsibility were significant positive predictors of vaccine acceptance, whereas elevated Complacency, Constraints, and Calculation reliably predicted underimmunization and delay.

Reliability

The psychometric evaluation of the 5C Scale demonstrated excellent internal consistency and stability across diverse validation samples.

Internal Consistency

In the foundational validation samples (encompassing university cohorts, mechanical Turk samples, and nationally representative adult panels), the 15-item instrument exhibited solid internal consistency across all five subscales:

• Confidence: Cronbach’s α = .82 – .88; McDonald’s ω = .84
• Complacency: Cronbach’s α = .78 – .84; McDonald’s ω = .81
• Constraints: Cronbach’s α = .77 – .85; McDonald’s ω = .80
• Calculation: Cronbach’s α = .76 – .81; McDonald’s ω = .78
• Collective Responsibility: Cronbach’s α = .71 – .77; McDonald’s ω = .74

Inter-item correlations within each three-item subscale fell reliably within the optimal range (.40 – .70), demonstrating targeted construct convergence without excessive semantic redundancy.

Test-Retest Stability

Longitudinal evaluations assessing test-retest reliability across multi-week intervals demonstrated high temporal stability for baseline latent constructs, with intraclass correlation coefficients (ICCs) ranging from .72 to .86. This stability ensures that the instrument captures enduring psychological dispositions rather than fleeting situational affect, while remaining sufficiently sensitive to detect authentic behavioral shifts following public health interventions.

Factor Analysis

The theoretical multidimensional architecture of the 5C scale was rigorously tested using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA).

Exploratory Factor Analysis (EFA)

During scale construction, initial item matrices were subjected to principal axis factoring with oblique (Promax) rotation to account for expected latent correlations among subdimensions. The empirical data strongly supported a five-factor extraction, decisively rejecting unidimensional and three-factor alternatives. All 15 items demonstrated robust primary factor loadings (λ > .60) onto their designated antecedents, with negligible cross-loadings (λ < .20 across secondary dimensions).

Confirmatory Factor Analysis (CFA)

Subsequent CFA performed on independent validation cohorts confirmed that the hypothesized five-factor oblique model exhibited superior goodness-of-fit indices compared to alternative structural specifications:

• Comparative Fit Index (CFI): .962 to .978 (exceeding the standard .95 threshold)
• Tucker-Lewis Index (TLI): .951 to .970 (exceeding the .95 threshold)
• Root Mean Square Error of Approximation (RMSEA): .041 to .052 (90% CI [.034, .059], meeting the < .06 criterion for close fit)
• Standardized Root Mean Square Residual (SRMR): .038 to .045 (meeting the < .08 criterion)

Nested model comparisons confirmed that collapsing Calculation into Confidence or merging Constraints with Complacency resulted in statistically significant deteriorations in model fit (Δχ² p < .001). Standardized factor loadings across all items ranged from .62 to .89, confirming clear parameter identification and measurement invariance across demographic subgroups.

Instrument / Measurement Tool

• Test Type: Standardized self-report psychometric rating scale
• Construct Dimensions: 5 orthogonal/correlated subscales (Confidence, Complacency, Constraints, Calculation, Collective Responsibility)
• Item Count: 15 items (long version) or 5 items (short version)
• Response Scale: 15 items (long version) or 5 items (short version)
• Standard Administration Anchors: 7-point Likert response options (1 = Strongly disagree, 2 = Moderately disagree, 3 = Slightly disagree, 4 = Neutral, 5 = Slightly agree, 6 = Moderately agree, 7 = Strongly agree)
• Target Population: General adult population (≥ 18 years); adaptable for adolescent and parental cohorts
• Administration Time: Standard 15-item version: 3–5 minutes; Short 5-item version: < 1 minute
• Scoring Procedure: Subscale scores are computed by calculating the unweighted arithmetic mean of the items comprising each antecedent:
• Confidence: Mean of items 1, 2, and 3
• Complacency: Mean of items 4, 5, and 6
• Constraints: Mean of items 7, 8, and 9
• Calculation: Mean of items 10, 11, and 12
• Collective Responsibility: Mean of items 13, 14, and 15
• Reverse-Coded Items: None. In the standard 15-item scale, all items are keyed directly toward higher levels of each respective construct. In the rapid 5-item screening format, items 1, 4, 7, 10, and 13 serve as the single-item index for each antecedent.

Permissions & Fee and Test Year

The 5C Scale of Psychological Antecedents of Vaccination was published in 2018. As an open-access scientific instrument published under the Creative Commons Attribution (CC BY 4.0) License via PLOS ONE, the scale is freely accessible to researchers, clinicians, non-governmental organizations, and public health authorities worldwide. No royalty fees or formal institutional licensing permissions are required for non-commercial or academic research applications, provided that appropriate bibliographic citation is accorded to the original authors (Betsch et al., 2018). Translations, cross-cultural adaptations, and digital survey integrations are permitted under the CC BY framework.

References

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• Betsch, C., Böhm, R., & Korn, L. (2013). Inviting free-riders or appealing to prosocial behavior? Game-theoretical reflections on communicating herd immunity in vaccine advocacy. Health Psychology, 32(9), 978–985. https://doi.org/10.1037/a0031590
• Betsch, C., Schmid, P., Heinemeier, D., Korn, L., Holtmann, C., & Böhm, R. (2018). Beyond confidence: Development of a measure assessing the 5C psychological antecedents of vaccination. PLOS ONE, 13(12), Article e0208601. https://doi.org/10.1371/journal.pone.0208601
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Items of the Scale