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The Intervention Mix Sevgi O. Aral Rome, Italy May 2010.

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Presentation on theme: "The Intervention Mix Sevgi O. Aral Rome, Italy May 2010."— Presentation transcript:

1 The Intervention Mix Sevgi O. Aral Rome, Italy May 2010

2 Ipsum lorem... !@#$%** *??


4 Single causes for disease states challenged by factors at multiple levels (biological, behavioral, group) health and disease interrelation among factors includes dynamic feedback + change

5 Solution: paragidm shift Public health complex system complex systems dynamic analytic approaches

6 Alassio, West Ligurian Riviera, Italy




10 Clustered risk behaviors Syndemics System of behaviors Net effect of behavior system Infection risk X

11 Sexual behaviors Prevention behaviors Risk compensation Disinhibition

12 Relationship among behaviors Conditional: condoms only with SWS Contextual: serosorting following accurate and honest disclosure

13 Relationship among behaviors Causal: Circumcision # of partners Concurrent partnerships condom use

14 Behavioral effects on incidence Synergistic Antagonistic Additive Duplicative conditional eg: risk of UAI with infected partner > risk of AI + risk of sex with infected partner

15 Complex system of behaviors Complex adaptive system of behaviors

16 Complex adaptive system? Complex system?

17 Complex System Interconnected parts Non-linear interactions Emergent properties

18 Complex adaptive systems Diverse Multiple interconnected elements Capacity to change Capacity to learn from experience

19 Examples Stock market Cell & developing embryo The brain The immune system

20 Behaviors of an individual = complex adaptive system

21 Living organisms – complex adaptive systems Multiple participating agents Hierarchical organization Extensive organization Extensive interactions among genetic and environmental effects Non-linear responses to perturbation Temporal dynamics of structure and function Distributed control Redundancy Compensatory mechanisms Emergent properties Rea et al., 2006

22 ... moving beyond the individual into the realm of social and policy processes must surely increase complexity of the causal process exponentially. Galea, et al., 2010

23 Complexity Complex adaptive systems Complexity science Health Medicine Health care

24 XX Newtonian science Positivism Scientism Reductionism Complexity science Complexity theory Complexity thinking


26 Health Medicine Health care delivery Individuals health [ (complex, interrelated, multi- level factors)]

27 STD/HIV epidemiology and prevention best described as complex adaptive systems Complex adaptive system of STD/HIV prevention interventions (CASSPI)

28 ... the emphasis in prevention research is shifting to evaluation of combination prevention packages in which synergies among interventions with modest levels of effect might lead to substantial efficacy overall.

29 Counseling and testing Condom use PMCT Concurrency Mass media interventions # partners Abstinence Microbidcides PREP Male circumcision duplicative, conditional, additive antagonistic or synergistic

30 Counseling and testing Condom use PMCT Concurrency Mass media interventions # partners Abstinence Microbidcides PREP Male circumcision

31 Multiple interventions from multiple professionals are provided concurrently. Interaction of interventions may significantly influence outcomes. The relatively small, nonsignificant effects of a simple intervention may be magnified when used in combination with other interventions. Interventions that seem effective in isolation may be antagonistic when provided together. In addition, effectiveness of combination of interventions is likely to be different for different patients. It is impossible for a randomized clinical trial to test all possible interactions among interventions encountered in routine practice. Horn, et al., 2007



34 Adherence during RCTs > Adherence during program rollout > Everyday adherence Adherence to single intervention > Adherence to multiple interventions

35 Timing of interventions Within developmental life course (individual) Within the epidemic trajectory (population)

36 Population level s in one subpopulation Compensatory s in other subpopulations s in sexual and drug use networks Unintended, unanticipated net effects

37 # FSW # new HIV infections # internet based FSW gonorrhea rates

38 Scott Cunningham – Baylor University Internet technology relative cost of advertisements relative cost of security indoor sex work market relative share of street work



41 Epidemiological context (sexual partner network- mixing-concurrency-heterogeneity) Intervention impact Epidemiological context Interactions among interventions

42 Context: economic, political, social environment + budget, organizational capacity, culture

43 Condom promotion: acceptable, effective # partners – MSM: politically unacceptable, ineffective Dr. Thomas Farley, New York City Health Commissioner

44 Intervention cost Available resources Resource allocation Cost effectiveness Comparative effectiveness

45 Coverage & Frequency Impact of interventions Dodd, et al., 2010

46 Required levels of coverage and frequency may be different for systems of interventions

47 Required coverage vs achievable coverage


49 POP I Trial Effects of single chlamydia test over 12 months overestimated Most cases of PID over 12 months not prevented by a single chlamydia screen Most cases of PID occurred in women who were negative for chlamydia at baseline Oakeshott, et al., BMJ, 2010

50 Policy makers might consider focusing on more frequent testing of those at higher risk, such as women with a new sexual partner or a recent history of chlamydial infection.

51 Targeting Who should receive prevention interventions? For chlamydia control Annual screening <25 USA <24 UK

52 Universal interventions For Highly network-dependent infections

53 The impact of many interventions can be amplified by targeting those that are most at risk of acquiring and transmitting infections. Garnett & Anderson 1995


55 Impact of targeted vaccination and behavioral interventions Impact of population-wide interventions Follow-up interventions targeting higher risk individuals enhance impact of widespread screening programs

56 Phase of the epidemic The extent to which targeting enhances intervention impact During earlier epidemic phases targeting high risk groups is particularly effective

57 Should all interventions target the same subpopulations?

58 Targeting Intervention frequency coverage Resources Costs Cost effectiveness Resource allocation Health system capacity

59 Duration Intensity

60 Sequencing of component interventions Layering of multi-level interventions


62 Copyright ©2010 American Public Health Association Frieden, T. R. Am J Public Health 2010;100:590-595 The health impact pyramid

63 Friedens Health Impact Pyramid focuses on: Health system infrastructure Societal composition Societal organization Societal operation

64 Copyright ©2010 American Public Health Association Frieden, T. R. Am J Public Health 2010;100:590-595 The health impact pyramid

65 Test and treat Screening and partner notification A B C (abstinence, be faithful, condom use) Counseling and testing

66 Prevention program perspective Test & treat Counseling & testing Screening & partner notification Target individual perspective A B C Serosorting and condom use

67 A systematic approach for Context appropriate complex adaptive intervention systems

68 Thank you!

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