Preventive medicine

Last updated: August 2, 2022

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Preventive medicine is the branch of medicine that deals not only with preventing disease from occurring, but also with halting disease progression and averting complications after disease onset. Disease prevention occurs on five levels, with measures ranging from health policies that affect the general population to specific treatments for particular patient groups: primordial prevention (actions that address environmental, socioeconomic, behavioral risk factors; e.g., smoking cessation campaigns), primary prevention (actions that inhibit the occurrence of specific diseases; e.g., immunization), secondary prevention (actions that inhibit the progress of specific diseases at an early stage to prevent or limit complications; e.g., screening), tertiary prevention (actions that inhibit the progress of specific diseases at an advanced stage to prevent or limit complications; e.g., blood pressure management in patients with hypertension), and quartenary prevention (actions that prevent over-medicalization and offer ethically acceptable interventions; e.g., pursuing nonaddictive strategies to managing chronic pain rather than prescribing opioids). One of the greatest challenges to preventive medicine is the “prevention paradox,” which states that preventive measures that benefit large populations have little impact on most people (e.g., even without measles immunization, only a relatively small proportion of the population would contract the disease). This leads to the common misconception that preventive measures provide no benefit to the individual as part of a larger population. Another challenge is poor medical adherence, i.e., the extent to which an individual follows prescribed drug regimens and medical advice, especially in patients who do not feel ill and, therefore, perceive the burden of prevention rather than its long-term benefits. Strategies to encourage adherence include a patient-centered approach, frequent follow-ups, and education regarding long-term consequences of medical conditions, behaviors, and lifestyle.

Public health interventions are actions and policies introduced by public health authorities to protect and improve the health of a population. Population-based practice focuses on the health concerns of entire populations and intervenes at the individual, community, and systemic levels.

Population-based public health interventions
Intervention Examples
Category System-focused Community-focused Individual-focused
Case finding and epidemiology
  • Surveillance (public health): collection, analysis, and interpretation of data required for planning and evaluation of public health interventions
  • Outreach: identifying at-risk populations and informing them about prevention, mitigation, and treatment
  • Case finding: identifying individuals and families with risk factors and providing them with educational resources and medical referrals
  • Health event and disease investigation: gathering data on reported threats to population health in order to develop control measures (see “Disease outbreak investigation”)
  • Screening: for identification of asymptomatic or at-risk individuals in a population
  • Creating hotlines during a pandemic to provide information to the general population and assist in mitigation and control measures
  • Establishing testing centers during a pandemic to identify cases in the community
  • Raising awareness during a pandemic and staying vigilant regarding pertinent symptoms in patients and colleagues
  • Monitoring local incidence and reporting data during health care worker staff meetings
Diagnosis and management
  • Referral and follow-up: directing individuals to health care resources and assessing outcomes
  • Case management: collaborating with individuals and providers to plan, coordinate, and assess care
  • Delegated functions: entrusting health care tasks to other authorized personnel
  • Developing school policies that implement new guidelines for children with asthma
  • Coordinating with the local chapter of the American Lung Association to organize regular asthma information events for students and parents
  • Creating an individualized management plan for a child recently diagnosed with asthma
Information, education, empowerment
  • Counseling: developing interpersonal rapport to facilitate coping and self-care
  • Consultation: deliberation between health care workers and/or experts on the diagnosis or treatment in any particular case
  • Health teaching: educating the public about health-related conditions and behaviors
  • Training physicians and midwives on latest research about the risks of alcohol use during pregnancy
  • Organizing meetings between a health care worker and the staff at a childcare center to develop a protocol to prevent measles outbreaks
  • Developing and distributing posters that aim to reduce alcohol use by women at establishments serving alcoholic beverages
  • Providing safer sex education at schools
  • Providing information about the impact of alcohol use on pregnancy for a reproductive health class in high schools
  • Providing fertility counseling for young couples at a free health clinic
Partnerships and networks
  • Collaboration: coordinating cooperation between institutions, groups, and/or individuals directed toward a particular health care goal
  • Community organizing: uniting individuals to identify and develop strategies to solve public health problems
  • Coalition building: developing alliances among organizations and institutions to solve public health problems
  • Collaborating with senior centers to provide screening of older adults for fall risk
  • Introducing a home safety checklist on fall prevention to residents of a senior center
  • Conducting home visits to the homes of older adults to assess risks and prevent falls
Policy development, promotion, and enforcement
  • Health advocacy: promoting public health through collaboration with community stakeholders and engagement with policymakers
  • Social marketing: deploying marketing techniques to positively influence a target audience's health behaviors
  • Policy development and enforcement: working with decision-makers to develop laws and regulations to protect and promote public health
  • Drafting legislation to mitigate certain risk factors, e.g.:
  • Carrying out an anti-bullying social media campaign in a school district
  • Providing free health care for persons experiencing homelessness
  • Organizing fundraising campaigns for orphan disease research
  • Providing reproductive health counseling to a sexually-active teenager
  • Definition: actions that address environmental, socioeconomic, and behavioral risk factors that affect a population as a whole to prevent potential disease or injury.
  • Measures [2][3]
    • Target: entire population
    • Health promotion beginning in childhood to encourage positive and discourage negative lifestyle habits
    • Mass education
    • Legislation
  • Examples
    • Programs on food safety and nutrition guidelines
    • Campaigns discouraging tobacco and drug use (e.g., smoke-free air laws in public buildings)
    • Building bicycle and sidewalks to promote physical activity

Primordial prevention aims to prevent risk factors from developing in the first place, whereas primary prevention targets existing risk factors to prevent the onset of a disease.

  • Definition: actions targeted at preventing specific diseases from occurring to decrease the incidence and, subsequently, the prevalence of those diseases
  • Measures [3][4]
    • Target: entire population and select groups (healthy individuals)
    • Decrease incidence and, in turn, prevalence of a specific disease
    • Primarily done through
      • Health promotion (health interventions, lifestyle modifications)
      • Environmental modifications (e.g., work safety)
      • Specific protection interventions (immunizations, chemoprophylaxis, safety of drugs and food)
  • Examples
Overview of preventive counseling [5]
Condition Approach Population Age group
Smoking cessation
  • Inquire about tobacco use and recommend cessation if the patient is a smoker.
  • Discuss consequences of smoking.
  • Provide information on smoking cessation strategies:
  • General population
  • Pregnant individuals
  • All age groups
Cardiovascular risk factors
  • Promote a healthy diet (rich in vegetables, fruit, whole grain, fiber, and protein; low in saturated fats, red meat, alcohol)
  • Promote physical activity (≥ 150 minutes of moderate-intensity activity or 75 minutes of high-intensity aerobic activity per week)
  • All adults
Sexually transmitted diseases (STDs)
  • Provide behavioral counseling to prevent sexually transmitted infections (e.g., counseling, decrease the number of sex partners, promote safer sex practices)
  • All sexually active individuals, esp. such who engage in risky sexual behavior (e.g., lack of condom use, multiple sex partners)
  • Individuals with diagnosis of STD
  • General population with onset of puberty (approx. 12 years of age)
  • All age groups
Substance use
  • Inquire about substance use and misuse of prescription drugs.
  • Use screening questionnaires
  • Recommend psychiatric treatment to patients with positive screening results.
  • All pregnant women
  • General population with onset of puberty (approx. 12 years of age)

Primary prevention helps to Prevent disease.

  • Definition: actions targeted at early detection of disease in asymptomatic patients (or while the symptoms of the condition are still mild) to promote early intervention
  • Measures [3]
    • Target: patient groups
    • Prevent further progression and complications from the disease
    • Consists of a two-step process: screening test to identify disease and follow-up for disease management

The screening recommendations covered below are primarily based on the USPSTF unless stated otherwise.

Screening complements diagnostics, but it is not a substitute.

Secondary prevention helps Screen.

Screening recommendations for nonpregnant women by age [5][6][7]
Age group Domain
Cardiovascular Malignancy Infection Other

18–45 years

45–50 years
50–55 years
55–60 years
60–65 years
65–70 years
70–75 years
75–80 years
  • Lung cancer: women with a ≥ 20 pack-year smoking history who either still smoke or quit within the last 15 years

For screening tests in transgender individuals, see: “Preventive health care of transgender individuals.”

Screening recommendations for men by age [5][6][7]
Age group Domain
Cardiovascular Malignancy Infection Other

18–45 years

  • None
45–50 years
50–55 years
55–60 years
60–65 years
65–70 years
70–75 years
75–80 years
  • Lung cancer: men with a ≥ 20 pack-year smoking history who either still smoke or quit within the last 15 years
Screening for cardiovascular disorders [5]
Condition Test Population group Age group Frequency
  • General population
  • ≥ 18 years
  • Every 3–5 years
  • Individuals at high risk for hypertension (e.g., patients with high to normal blood pressure or obesity)
  • ≥ 40 years
  • Every 1–2 years
Hyperlipidemia [6]
  • General population
  • 40–75 years
  • Every 5 years
  • 20-39 years
  • No specific recommendation
Abdominal aortic aneurysm [8]
  • 65–75 years
  • Once
Screening for endocrinological disorders [5][7]
Condition Test Population group Age group Frequency

Diabetes mellitus

  • General population
  • > 45 years
  • Every 3 years
  • < 45 years
  • All age groups
  • Annual
  • Individuals with HIV
  • All age groups
  • Before and 3–6 months after initiating or switching antiretroviral therapy, then annually if results remain normal
  • N/A
  • All women
  • ≥ 65 years
  • Once
  • < 65 years
  • No specific recommendation
Screening for cancer [5][9]
Condition Test Population group Age group Frequency
Colorectal cancer
  • General population
  • 45–75 years
  • Every 10 years
  • Every 1–2 years
  • > 10 years
  • Annual
  • > 20 years
  • Every 1–2 years
  • General population
  • 45–75 years
  • Every 5 years
  • General population
  • 45–75 years
  • General population
  • 45–75 years
  • Annual
Breast cancer [10][11][12]
  • Women
  • Every 2 years
  • ≥ 25 years
  • Annual
  • ≥ 30 years
  • Annual
Lung cancer
  • Individuals with a ≥ 20 pack-year smoking history who either still smoke or quit within the last 15 years
  • 50–80 years
  • Annually for up to 3 years
Cervical cancer
  • Women
  • 21–65 years
  • Every 3 years
  • Women
  • 30–65 years
  • Every 5 years
  • Women
  • 30–65 years
  • Every 5 years
Screening for infectious diseases [5][13]
Condition Test Population group Age group Frequency
HIV [14]
  • General population
  • 13–65 years
  • Once
  • All ages
  • Annual
  • Pregnant women
  • N/A

Hepatitis B

  • No specific recommendation
  • Pregnant women
  • N/A
  • First prenatal visit
Hepatitis C
  • All adults
  • < 80 years
  • Once
  • Regular screening for individuals at high risk
  • Pregnant women
  • N/A
  • First prenatal visit
  • All sexually active women
  • ≤ 24 years
  • > 24 years
  • Pregnant women
  • N/A
  • First prenatal visit
  • All age groups
  • Every 3 months
  • Pregnant women
  • N/A
  • First prenatal visit
Asymptomatic bacteriuria
  • Pregnant women
  • N/A
  • First prenatal visit
Overview [5][9]
Condition Test Population group Age group Frequency
Rh incompatibility
  • Pregnant women
  • All age groups
  • First prenatal visit
  • Repeat at 24–28 weeks gestation if the initial screening result was Rh-positive.

Major depressive disorder

  • 12–18 years
  • Annual
  • General adult population (including pregnant and postpartum women)
  • All age groups
  • No specific recommendation; at least once
  • Children
  • 3–5 years
  • Once
Intimate partner violence
  • All women of reproductive age
  • There are no specific recommendations on screening for other population groups.
  • No specific recommendation

Tertiary prevention helps Treat.

  • Definition: actions taken to avoid unnecessary medical interventions by identifying actions that might cause harm rather than benefit patients
  • Measures [3][15][16]
    • Target: patient groups
    • Prevent overmedicalization (e.g., overdiagnosis, overtreatment)
    • Avoid unnecessary diagnostic studies or treatments without proven efficacy (e.g., only offer ethically acceptable interventions, use treatments previously assessed by randomized controlled trial with low risk of bias)
    • Avoid disease mongering, i.e., widening the definition of certain medical illnesses, to expand markets for those who deliver and/or sell medical treatments.
  • Examples [17]

QUaternary prevention helps sQUeeze out unnecessary treatments.

  • Definition: the degree to which an individual follows prescribed medication regimens and medical advice [18]
  • Common reasons for poor adherence [19][20]
    • Medication
      • Forgetfulness (mostly occurs in older patients or patients with cognitive disabilities)
      • Financial burden (e.g., cost of medications)
      • Polypharmacy (e.g., multiple comorbidities, complex treatment regimen)
      • Poor education by health care provider regarding medication use, side effects, and consequences of poor adherence
      • Among adolescents: fear of stigma due to peer attitudes toward the illness and/or its treatment [21]
    • Lifestyle modification: lack of motivation
    • Cultural and personal beliefs
      • Personal health care beliefs (e.g., homeopathy)
      • Personal health care misconceptions (e.g., vaccine hesitancy)
      • Distrust of health care system
  • Strategies to encourage adherence
    • Identify potential barriers (e.g., disease-related knowledge)
    • A patient-centered approach
    • Communication about treatment options
    • Provide patient education
      • Written instructions regarding medication
      • Discuss medication side effects
      • Confirm the patient's understanding of the treatment instructions using the teach-back method. [22]
    • Reminder system
      • Regular follow-up visits
      • Email reminder programs
      • Electronic alerts
      • Phone call reminders
    • Peer-facilitated behavioral interventions to convey knowledge about the illness and social acceptance for its treatment [23][24]
      • Encourage adolescents with chronic illnesses to familiarize their peers with their illness and its treatment (e.g., an adolescent with type 1 diabetes mellitus may carry out routine insulin injections in the presence of their peers).
      • Encourage patients with chronic illnesses to seek support from peers with the same chronic illness (e.g., through online communities).
  • Definition [25][26]
    • A preventive measure that benefits a population as a whole will offer little benefit to each individual member of that population (population approach to prevention; primordial and primary prevention)
    • A preventive measure that benefits a group of individuals susceptible to a particular disease will offer little benefit to the population as a whole (high-risk approach to prevention; secondary and tertiary prevention).
    • The high-risk approach and the population approach to prevention are complementary, but preventive medicine should prioritize preventing the underlying causes of disease (primordial and primary prevention) over reducing the impact of disease after it occurs (secondary and tertiary prevention).
    • The prevention paradox may lead to the misconception that a measure that provides no immediate benefit to the individual, provides no benefit to the entire population and that a small risk involved in a measure (e.g., vaccination) outweighs the benefits of that measure.
  • Examples
    • While heavy drinking carries a greater risk than moderate drinking, moderate drinking has a greater negative impact on the general population because the number of moderate drinkers is greater than that of heavy drinkers.
    • Seatbelt laws have prevented many severe injuries, yet the overall risk of dying in an accident due to not wearing a seatbelt is still low.
  • Definitions
    • Disease cluster: an unusual aggregation, real or perceived, of cases of a disease that are grouped together in time and space
    • Disease outbreak: the sudden occurrence of more cases of a disease than expected in a given area, population, and/or season
  • Indentifying outbreaks
    • Outbreaks are identified by health authorities through reports that may come from hospitals, laboratories, health care providers, and even the general population.
    • After receiving an initial report, health authorities decide on whether to investigate further.
  • Investigating outbreaks
    • Field investigation involves identifying a potential disease outbreak, forming a hypothesis about its cause, gathering data to test the hypothesis, and finally, developing and implementing control and prevention measures.
    • Steps of the field investigation usually include:
      • Preparing for the investigation
        • Gathering information about the condition, area, and/or population of interest
        • Organizing a team and necessary supplies
      • Confirming the outbreak
      • Establishing a case definition
      • Finding cases and documenting details of each case
      • Developing a hypothesis about the cause of the outbreak
      • Analyzing the gathered data and evaluating the hypothesis
      • Comparing and reconciling with laboratory and/or environmental studies
      • Developing and implementing control and prevention measures
      • Initiating or maintaining surveillance.
      • Communicating the findings to the public
  • The Whole School, Whole Community, Whole Child (WSCC) model is a student-centered framework developed by the CDC for addressing health in schools.
  • WSCC consists of ten components:
    • Physical education and physical activity
      • Physical activity recommendations are outlined in the Comprehensive School Physical Activity Program, which consists of five components: physical education, physical activity during school, physical activity before and after school, staff involvement, and family and community engagement.
      • Physical education is an academic subject for all K-12 students, which helps to develop motor skills, knowledge, and behaviors for a healthy lifestyle.
    • Nutrition environment and services
      • Food provided to students must meet the Nutrition Standards for School Meals issued by the USDA.
      • Free drinking water must be available to all students throughout the day.
      • The National School Lunch and Breakfast Programs provide nutritious, low-cost or free meals to children each school day.
    • Health education: Integration of health education into the curriculum involves addressing topics such as nutrition, mental health, sexual health, violence prevention, and the use of alcohol, tobacco, and other substances in a variety of subjects and educational settings.
    • Social and emotional climate: A positive emotional climate is essential for proper child development and should be maintained in all aspects of school functioning.
    • Physical environment: School buildings and surrounding environment should be safe from any health threat (e.g., traffic, crime, construction, improper ventilation).
    • Health services: Services from qualified health professionals (e.g., nurses, physicians, physician assistants) should be available to all students.
    • Counseling, psychological, and social services: prevention and intervention to support the mental, behavioral, and social health of students (i.e., with certified school counselors, school psychologists, and school social workers)
    • Employee wellness: School employees should have access to programs, policies, and benefits that promote their health and well-being.
    • Community involvement: partnerships with local groups, organizations, and businesses to encourage students' civic engagement and to share school resources (e.g., school-based health centers and sports facilities) with the community
    • Family engagement: continuous involvement of students' families in educational activities and development
  1. Essential Evidence on a page: No 109 The prevention paradox and population strategies applied to transport. Updated: November 13, 2014. Accessed: December 18, 2019.
  2. Rose G. Strategy of prevention: lessons from cardiovascular disease.. BMJ. 1981; 282 (6279): p.1847-1851. doi: 10.1136/bmj.282.6279.1847 . | Open in Read by QxMD
  3. ANONIMO, de la santé Om, Organization WH, Who WH. Adherence to Long-term Therapies. World Health Organization ; 2003
  4. Best ways to deal with noncompliant patients.
  5. Stevenson FA et al.. A systematic review of the research on communication between patients and health care professionals about medicines: the consequences for concordance. Health Expectations. 2004; 7 (3): p.235-245. doi: 10.1111/j.1369-7625.2004.00281.x . | Open in Read by QxMD
  6. Hanghøj S, Boisen KA. Self-Reported Barriers to Medication Adherence Among Chronically Ill Adolescents: A Systematic Review. Journal of Adolescent Health. 2014; 54 (2): p.121-138. doi: 10.1016/j.jadohealth.2013.08.009 . | Open in Read by QxMD
  7. Use the Teach-Back Method: Tool #5. Updated: September 1, 2020. Accessed: October 29, 2021.
  8. Enriquez M, Conn VS. Peers as Facilitators of Medication Adherence Interventions: A Review.. Journal of primary care & community health. 2016; 7 (1): p.44-55. doi: 10.1177/2150131915601794 . | Open in Read by QxMD
  9. Pai AL, McGrady M. Systematic review and meta-analysis of psychological interventions to promote treatment adherence in children, adolescents, and young adults with chronic illness.. J Pediatr Psychol. 2014; 39 (8): p.918-31. doi: 10.1093/jpepsy/jsu038 . | Open in Read by QxMD
  10. Lancarotte I, Nobre M. Primordial and primary prevention programs for cardiovascular diseases: from risk assessment through risk communication to risk reduction. A review of the literature. Clinics. 2016; 71 (11): p.667-678. doi: 10.6061/clinics/2016(11)09 . | Open in Read by QxMD
  11. Kisling LA, M Das J. Prevention Strategies. StatPearls. 2020 .
  12. USPSTF A and B Recommendations.. Updated: September 1, 2019. Accessed: October 7, 2019.
  13. Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation. 2018; 139 (25). doi: 10.1161/cir.0000000000000625 . | Open in Read by QxMD
  14. Owens DK et al.. Screening for Abdominal Aortic Aneurysm. JAMA. 2019; 322 (22): p.2211. doi: 10.1001/jama.2019.18928 . | Open in Read by QxMD
  15. Crider KS, Bailey LB, Berry RJ. Folic Acid Food Fortification—Its History, Effect, Concerns, and Future Directions. Nutrients. 2011; 3 (3): p.370-384. doi: 10.3390/nu3030370 . | Open in Read by QxMD
  16. Technical Contributors to the June 2018 WHO meeting. A definition for community-based surveillance and a way forward: results of the WHO global technical meeting, France, 26 to 28 June 2018. Eurosurveillance. 2019; 24 (2). doi: 10.2807/ . | Open in Read by QxMD
  17. Principles of Epidemiology in Public Health Practice, Third Edition. Lesson 6: Investigating an Outbreak. Updated: September 15, 2016. Accessed: January 7, 2022.
  18. Keller LO, Strohschein S, Lia-Hoagberg B, Schaffer MA. Population-Based Public Health Interventions: Practice-Based and Evidence-Supported. Part I. Public Health Nurs. 2004; 21 (5): p.453-468. doi: 10.1111/j.0737-1209.2004.21509.x . | Open in Read by QxMD
  19. Whole School, Whole Community, Whole Child (WSCC). Updated: March 23, 2021. Accessed: January 6, 2022.
  20. Mauch KF. Mksap 17 General Internal Medicine. American College of Physicians ; 2016
  21. Siu AL; U.S. Preventive Services Task Force. Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement.. Annals of Internal Medicine. 2016 .
  22. American College of Obstetricians-Gynecologists. Practice Bulletin No 182: Hereditary Breast and Ovarian Cancer Syndrome. Obstetrics & Gynecology. 2017; 130 (3): p.e110-e126. doi: 10.1097/aog.0000000000002296 . | Open in Read by QxMD
  23. Monticciolo DL, Newell MS, Moy L, Niell B, Monsees B, Sickles EA. Breast Cancer Screening in Women at Higher-Than-Average Risk: Recommendations From the ACR. J Am Coll Radiol. 2018; 15 (3): p.408-414. doi: 10.1016/j.jacr.2017.11.034 . | Open in Read by QxMD
  24. Bibbins-Domingo K, Grossman DC, et al. Screening for Syphilis Infection in Nonpregnant Adults and Adolescents. JAMA. 2016; 315 (21): p.2321. doi: 10.1001/jama.2016.5824 . | Open in Read by QxMD
  25. Branson BM, Handsfield HH, Lampe MA et al. Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings. MMWR Recomm Rep. 2006; 55 (RR14): p.1-17.
  26. Martins C et al.. Quaternary prevention: reviewing the concept. Eur J Gen Pract. 2018; 24 (1): p.106-111. doi: 10.1080/13814788.2017.1422177 . | Open in Read by QxMD
  27. Pandve HT. Quaternary prevention: need of the hour.. Journal of family medicine and primary care. undefined; 3 (4): p.309-10.
  28. Alber K, Kuehlein T, Schedlbauer A, Schaffer S. Medical overuse and quaternary prevention in primary care – A qualitative study with general practitioners. BMC Fam Pract. 2017; 18 (1). doi: 10.1186/s12875-017-0667-4 . | Open in Read by QxMD
  29. American Diabetes Association. 2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes—2021. Diabetes Care. 2020; 44 (Supplement 1): p.S15–S33. doi: 10.2337/dc21-S002 . | Open in Read by QxMD
  30. US Preventive Services Task Force., Davidson KW, Barry MJ, et al. Screening for Prediabetes and Type 2 Diabetes: US Preventive Services Task Force Recommendation Statement.. JAMA. 2021; 326 (8): p.736-743. doi: 10.1001/jama.2021.12531 . | Open in Read by QxMD
  31. Newberger DS. Down Syndrome: Prenatal Risk Assessment and Diagnosis. American Family Physician. 2000 .
  33. Joshi SN. Hepatitis C screening.. The Ochsner journal. undefined; 14 (4): p.664-8.

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