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The Intervention Mix Sevgi O. Aral Rome, Italy May 2010 Ipsum lorem . . . !@#$%** *?? Single causes for disease states challenged by → factors at multiple levels (biological, behavioral, group) health and disease → interrelation among factors includes dynamic feedback + change Solution: paragidm shift Public health ≡ complex system → complex systems dynamic analytic approaches Alassio, West Ligurian Riviera, Italy Multiple Partners Casual Partners Concurrent Partners Condom Use Age at Sexual Debut Transactional Sex Drug Use Forced Sex Clustered risk behaviors Syndemics System of behaviors Net effect of behavior system Infection risk X Sexual behaviors Prevention behaviors Risk compensation Disinhibition Relationship among behaviors Conditional: condoms only with SWS Contextual: serosorting following accurate and honest disclosure Relationship among behaviors Causal: Circumcision →↑ # of partners Concurrent partnerships →↑ condom use 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 Complex system of behaviors Complex adaptive system of behaviors Complex adaptive system? Complex system? Complex System • Interconnected parts • Non-linear interactions • Emergent properties Complex adaptive systems • Diverse • Multiple interconnected elements • Capacity to change • Capacity to learn from experience Examples • Stock market • Cell & developing embryo • The brain • The immune system Behaviors of an individual = complex adaptive system 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 “ . . . 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 Complexity Complex adaptive systems Complexity science Health Medicine Health care Newtonian science Complexity science Positivism Complexity theory XX Scientism Reductionism Complexity thinking Health Medicine Health care delivery Individual’s health [d (complex, interrelated, multilevel factors)] STD/HIV epidemiology and prevention best described as complex adaptive systems Complex adaptive system of STD/HIV prevention interventions (CASSPI) “ . . . 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.” ↓ Concurrency ↓ # partners Test and treat Counseling and testing Mass media interventions PMCT Microbidcides Condom use Abstinence → duplicative, conditional, additive ← antagonistic or synergistic PREP Male circumcision ↓ Concurrency ↓ # partners Test and treat Counseling and testing Mass media interventions PMCT Abstinence Microbidcides Condom use PREP Male circumcision “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 Adherence during RCTs > Adherence during program rollout Adherence to single intervention > > Everyday adherence Adherence to multiple interventions Timing of interventions → Within developmental life course (individual) → Within the epidemic trajectory (population) Population level Ds in one subpopulation Compensatory Ds in other subpopulations Ds in sexual and drug use networks Unintended, unanticipated net effects ↑ # FSW → ↓ # new HIV infections ↑ # internet based FSW → gonorrhea rates Scott Cunningham – Baylor University Internet technology → ↓ relative cost of advertisements ↓ relative cost of security ↑ indoor sex work market ↓ relative share of street work Epidemiological context (sexual partner networkmixing-concurrency-heterogeneity) Intervention impact Epidemiological context Interactions among interventions Context: economic, political, social environment + budget, organizational capacity, culture Condom promotion: acceptable, effective ↓ # partners – MSM: politically unacceptable, ineffective Dr. Thomas Farley, New York City Health Commissioner Intervention cost Available resources Resource allocation Cost effectiveness Comparative effectiveness Coverage & Frequency ↓ Impact of interventions Dodd, et al., 2010 Required levels of coverage and frequency may be different for systems of interventions Required coverage vs achievable coverage 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 “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.” Targeting “Who should receive prevention interventions?” For chlamydia control Annual screening <25 — USA <24 — UK Universal interventions For Highly network-dependent infections “The impact of many interventions can be amplified by targeting those that are most at risk of acquiring and transmitting infections.” Garnett & Anderson 1995 → 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 Phase of the epidemic The extent to which targeting enhances intervention impact → During earlier epidemic phases targeting high risk groups is particularly effective Should all interventions target the same subpopulations? Resources Targeting Intervention frequency coverage Costs Cost effectiveness Resource allocation Health system capacity Duration Intensity Sequencing of component interventions Layering of multi-level interventions The health impact pyramid Frieden, T. R. Am J Public Health 2010;100:590-595 Copyright ©2010 American Public Health Association Frieden’s Health Impact Pyramid focuses on: Health system infrastructure Societal composition Societal organization Societal operation The health impact pyramid Frieden, T. R. Am J Public Health 2010;100:590-595 Copyright ©2010 American Public Health Association Test and treat Screening and partner notification A B C (abstinence, be faithful, condom use) Counseling and testing Prevention program perspective Test & treat Counseling & testing Screening & partner notification Target individual perspective ABC Serosorting and condom use A systematic approach for “Context appropriate complex adaptive intervention systems” Thank you!