Key Public Health Models

Why This Matters

Public health models aren't just abstract theories—they're the frameworks that determine how we understand disease, design interventions, and allocate resources. When you're tested on these models, you're being asked to demonstrate that you understand why certain interventions work at certain levels, how behavior change actually happens, and what factors create health disparities in the first place. These models show up repeatedly in exam questions because they represent the foundational thinking behind every public health program you'll encounter.

The key insight here is that different models answer different questions. Some explain individual behavior (why does someone choose to smoke or get vaccinated?), others explain disease dynamics (how does an outbreak spread?), and still others explain systemic factors (why do some communities have worse health outcomes?). Don't just memorize the model names—know what type of question each model helps answer and when you'd apply it in practice.

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Individual Behavior Models

These models focus on the psychological and cognitive factors that drive personal health decisions. They assume that understanding individual beliefs, perceptions, and readiness to change is essential for designing effective health interventions.

Health Belief Model

• Perceived susceptibility and severity—individuals must believe they're at risk for a condition and that the condition is serious enough to warrant action
• Perceived benefits vs. barriers—behavior change happens when people believe the benefits of action outweigh the obstacles to taking that action
• Best for health education campaigns—use this model when designing messaging that targets individual beliefs about screening, vaccination, or preventive behaviors

Stages of Change (Transtheoretical) Model

• Five distinct stages—precontemplation, contemplation, preparation, action, and maintenance represent a person's readiness to adopt new behaviors
• Change is non-linear—the model explicitly accounts for relapse as a normal part of behavior change, not a failure
• Tailored interventions—match your approach to the person's current stage; someone in precontemplation needs different messaging than someone in preparation

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Multi-Level Influence Models

These models recognize that health outcomes result from factors operating at multiple levels simultaneously. They reject the idea that health is purely an individual responsibility and instead map the complex web of influences on behavior and outcomes.

Socio-Ecological Model

• Four nested levels of influence—individual, relationship, community, and societal factors all shape health behaviors and outcomes
• Multi-level interventions required—effective public health strategies must address factors at multiple levels simultaneously, not just target individuals
• Widely used framework—this model underlies most contemporary public health program design and appears frequently on exams

Social Determinants of Health Model

• Conditions of daily life—focuses on where people are born, grow, live, work, and age as the primary drivers of health outcomes
• Upstream factors—emphasizes socioeconomic status, education, housing, and environment as root causes of health disparities
• Policy-level solutions—argues that addressing health inequities requires structural and policy interventions, not just individual behavior change

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Disease Transmission Models

These models explain how diseases spread and persist in populations. They provide the conceptual foundation for epidemiological investigation and outbreak response.

Epidemiological Triad

• Three interacting components—agent (pathogen or cause), host (susceptible individual), and environment (conditions enabling transmission)
• Dynamic equilibrium—disease occurs when the balance between these three components shifts; interventions can target any component
• Foundation of outbreak investigation—this classic model guides how epidemiologists identify points of intervention during disease outbreaks

One Health Model

• Interconnected health domains—recognizes that human, animal, and environmental health are fundamentally linked and cannot be addressed in isolation
• Zoonotic disease focus—essential for understanding diseases that jump between species, including emerging infectious diseases like COVID-19
• Cross-sector collaboration—requires veterinarians, physicians, ecologists, and public health professionals to work together

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Program Planning Models

These models guide the systematic development, implementation, and evaluation of public health interventions. They provide step-by-step frameworks for translating theory into practice.

PRECEDE-PROCEED Model

• Two-phase structure—PRECEDE assesses needs and identifies predisposing, reinforcing, and enabling factors; PROCEED guides implementation and evaluation
• Evidence-based planning—forces program designers to conduct thorough assessments before jumping to interventions
• Comprehensive evaluation built in—includes process, impact, and outcome evaluation as integral components, not afterthoughts

Health Impact Pyramid

• Five tiers of intervention—from bottom to top: socioeconomic factors, changing context, long-lasting protective interventions, clinical interventions, counseling/education
• Base has greatest population impact—interventions addressing socioeconomic factors affect the most people with the least individual effort required
• Inverse relationship—as you move up the pyramid, interventions require more individual effort but reach fewer people

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Systems-Level Models

These models take the broadest view, conceptualizing public health as operating within complex, interconnected systems. They emphasize collaboration, equity, and comprehensive approaches to population health.

Public Health 3.0 Model

• Beyond traditional public health—expands the role of health departments to serve as Chief Health Strategists for their communities
• Cross-sector partnerships—emphasizes collaboration with housing, education, transportation, and other sectors that influence health
• Health equity focus—explicitly centers equity and community engagement as core principles, not add-ons

Systems Thinking in Public Health

• Complex adaptive systems—views health issues as emerging from interconnected components with feedback loops, delays, and unintended consequences
• Relationships over components—focuses on understanding how factors interact rather than just identifying individual risk factors
• Avoids reductionism—recognizes that intervening on one part of the system may have ripple effects throughout

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Quick Reference Table

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Self-Check Questions

1. Which two models both address individual-level behavior change, and how do they differ in their approach to intervention design?

2. If you were investigating a new zoonotic disease outbreak, which two models would be most relevant, and what would each contribute to your analysis?

3. Compare the Socio-Ecological Model and the Health Impact Pyramid—how does each model conceptualize the relationship between individual and structural factors?

4. A community has high rates of diabetes linked to food insecurity and lack of safe spaces for physical activity. Using the Social Determinants of Health framework, identify three upstream factors to target. Why might individual counseling alone be insufficient?

5. You're designing a smoking cessation program and discover that most participants aren't yet considering quitting. Which model tells you this matters, and how would you adjust your intervention approach?