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

Condom Use Number of Partners

Sex Work

Casual PartnersMultiple Partners

Early Age at Sexual Debut

Concurrent PartnersShort Gaps

Same Sex Partners

Condom Use

Transactional Sex

Drug Use

Casual PartnersMultiple Partners

Age at Sexual Debut

Concurrent Partners

Forced Sex

Condom Use

Transactional Sex

Drug Use

Casual PartnersMultiple Partners

Age at Sexual Debut

Concurrent Partners

Forced Sex

Clustered risk

behaviorsSyndemics

System of

behaviors

Net effect of

behavior

system

Infection

risk

X

Sexual behaviors

Prevention behaviors

Risk compensationDisinhibition

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

ComplexityComplex adaptive systems

Complexity science

HealthMedicine

Health care

XX

Newtonian science

Positivism

Scientism

Reductionism

Complexity science

Complexity theory

Complexity thinking

Health

Medicine

Health care delivery

Individual’s health[d (complex, interrelated, multi-

level 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.”

Counseling and testing

Condom use

PMCT

↓ Concurrency

Mass media interventions

↓ # partners

Abstinence

Microbidcides

PREP

Male circumcision

Test and treat

→ duplicative, conditional, additive← antagonistic or synergistic

Counseling and testing

Condom use

PMCT

↓ Concurrency

Mass media interventions

↓ # partners

Abstinence

Microbidcides

PREP

Male circumcision

Test and treat

“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

Adherenceduring RCTs > Adherence

during program rollout

> Everyday adherence

Adherence to single intervention > 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 network-mixing-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?

Targeting

Intervention frequency

coverage

Resources

Costs

Cost effectiveness

Resource allocation

Health system capacity

Duration

Intensity

Sequencing of component interventions

Layering of multi-level interventions

Copyright ©2010 American Public Health Association

Frieden, T. R. Am J Public Health 2010;100:590-595

The health impact pyramid

Frieden’s Health Impact Pyramid focuses on:

Health system infrastructure

Societal composition

Societal organization

Societal operation

Copyright ©2010 American Public Health Association

Frieden, T. R. Am J Public Health 2010;100:590-595

The health impact pyramid

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

A B C

Serosorting and condom use

A systematic approach

for

“Context appropriate complex adaptive intervention systems”

Thank you!