Peter PiotInstitute for Global Health

4th December 2009

What I wish modelling could do for global health

Colonial Post-colonial End of cold war Globalisation

Tropical medicine

Geographic medicine

International Health

Global Health

[i] 1996-2005 data: Extracted from 2006 Report on the Global AIDS Epidemic (UNAIDS, 2006)[ii] 1986-1993 data: AIDS in the World II. Edited by Jonathan Mann and Daniel J. M. Tarantola (1996)

Notes: [1] 1986-2000 figures are for international funds only [2] Domestic funds are included from 2001 onwards

Funding Total annual resources available for AIDS, 1986 ‒2007

Funding Total annual resources available for AIDS, 1986 ‒2007

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

US$ million

2921623

8.3 billion

Signing of Declaration of Commitment on HIV/AIDS, UNGASS

‘96 ‘97 ‘98 ‘99 ‘00 ‘01 ‘02 ‘03 ‘04 ‘051986 ‘87 ‘88 ‘89 ‘90 ‘91 ‘92 ‘93 ‘94 ‘95

Less than US$ 1 million

59 212

World BankMAP launch

Global Fund

PEPFAR

257

UNAIDS Gates

Foundation

‘06 2007

10 000

8.9 billion

10 billion

Modelling for Global Health

• Interpretation• Prediction and anticipation• Creation of hypothesis• Implications of policy options• Evaluation • Identification of data needs• Advocacy

Behavioural change, impact in urban and semi-urban Zimbabwe

1980 1985 1990 1995 2000 2005 20100

10

20

30

40

50

60

Year

HIV

pre

vale

nce

(%

)

1980 1985 1990 1995 2000 2005 20100

2

4

6

8

10

Year

HIV

inci

de

nce

(p

er

10

0p

yar)

Source: Hallett TB, et al. Epidemics 2009;1(2):108-117

Natural decline in incidence ~1990

Accelerated decline in incidence, due to behaviour change ~2000

M0: without behavioural change

M1: assuming behavioural change, better fit to surveillance data

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Male clients Sex workers Wife from husband Husband from wife Mother to child

Cambodia, 1988-2004

Number of new HIV infections by route of transmission

Source: Peerapatanapokin and Brown, using Asia Epidemic Model

Real-time modelling

• FMD, SARS showed the potential of real-time modelling (statistical and dynamical).

• Initial goal – ‘now-casting’ – correcting for censorship/delays in case/mortality reporting

• Aims – estimate R, mortality, generation time distribution, predict future trends, evaluate sufficiency of control measures.

• Important new approach – inferring infection trees – developed in 2001 then further in 2003 for SARS.

• Require data though – need to set realistic expectations.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

25-Feb

11-Mar

25-Mar

8-Apr

22-Apr

6-May

20-May

3-Jun

17-Jun

1-Jul

End of week

Par

amet

er v

alu

e

R

R0

b

R 0

R

I

1

2 5

3

7

6

8

9 10

4

Prediction and anticipation

World population by age groups, 1950-2050

Source: United Nations Population Division 2006. “World Population Prospects: The 2006 Revision”

Predicted expansion of dengue in Africa

1990 2085

This projection uses an scenario that delivers a three fold increase in CO2 by 2100

Source: Hales S et al. Lancet. 2002;360(9336),830-834.

Geographic origins of emerging infectious diseases events from 1940 to 2004

Source: Jones KE et al. Nature 2008:451;990-993.

AIDS spending (share of gross domestic product) and adult HIV prevalence in 2030

Source: Hecht R et al. Health Affairs 2009;28(6):1591-1605

Population impact of treatment as prevention

Source: Granich RM, et al. Lancet 2009; 373: 48–57.

Time trends resulting from application of universal voluntary HIV testing and immediate ART strategy for people who test HIV positive, in combination with

other adult prevention interventions that reduce incidence by 40%

Policy impact of treatment as prevention

Source: Bulletin des médecins suisses | Schweizerische Årztezeitung | Bolletino dei medici svizzeri | 2008;89:5 and www.hivandhepatitis.com

Policy options

Hep B vaccination strategies in the Netherlands

Source: Kretzschmar M et al. Lancet Infectious Diseases 2008;8(2):85-87 .

Will it be possible to increase coverage of risk groups to acceptable levels or is universal vaccination the way to ensure satisfactory vaccination coverage of high-risk groups?

Universal vaccination of all neonates or all adolescents has the greatest potential at the cost of having to vaccinate large numbers of individuals

Targeting vaccination to high-risk groups can be cost effective, despite being demanding in effort and logistics.

HPV vaccination - need for continued screening and appropriate health-care messages

Source: Garnett GP et al. Vaccine 2006;24(3):S178-S186.

Long term view: Effects of Prevention on Future Costs of ART

$0$2$4$6$8

$10$12$14$16

2005 2010 2015 2020 2025 2030

Billion US$

Current Prevention Scaled Up Prevention

Interaction of circumcision interventions with existing behaviour change programmes

Source: Hallett TB, et al. PLoS ONE 2008;3(5): e2212

Projected effect of different prevention interventions on HIV incidence

Source: Jansen VAA, et al. Science 2003;301:904.

Measles outbreaks in a population with declining vaccine uptake

Synergy needed

• Science• Politics• Money• Programme delivery

Source: Koplan JP et al. Lancet 2009;373:1993.

Recorded female deaths in South Africa and Brazil for ages 15-64 years

Source: Nathan Geffen. Statistics South Africa and Instituto Brasileiro de Geografia e Estatistica.

Brazil, 2004. South Africa, 1997. South Africa, 2004

Need for real-life effectiveness evaluations

Seguro Popular is a new set of health reforms aiming to provide health coverage to 50 million uninsured Mexicans.

23% reduction from baseline in catastrophic expenditures

30% reduction in poor households and 59% in experimental compliers

Source: King G et al. The Lancet 2009: 373(9673):1447-1454

Concurrent partnerships have been hypothesised as one of the main factors behind the HIV epidemics in sub-Saharan Africa for the past 15 years, with empirical evidence providing different conclusions.

It was only a few days ago that the Working Group on Measuring Concurrent Sexual Partnerships (UNAIDS Reference Group on Estimates, Modelling, and Projections) published a consensus paper on indicators for concurrency .

The Lancet, article in press: doi:10.1016/S0140-6736(09)62040-7

Data Needs: Concurrency and HIV

Source: Morris M et al. AIDS 1997;11(5):641-648.

Source: Bollinger et al. Journal of the International AIDS Society 2009 12:7.

Total net cost of male circumcision programme (US dollars)

Advocacy : cost and impact of male circumcision

New adult HIV infections by scenario

A new agenda for global healthNew challenges for modellers

• Finalize the unfinished agenda!• Chronic diseases and mental health• Population growth, climate change, urbanization,

water• Deliver new prevention& treatment technologies• More effective health systems

Projected deaths by cause for high-, middle-, and low-income countries

Source: WHO World Health Statistics 2008 http://www.who.int/whosis/whostat/EN_WHS08_Full.pdf

Network analysis of obesity in the Framingham cohort

Source: Christakis NA et al. NEJM 2007:357(4);370-379.

Largest connected subcomponent of the social network in the Framingham Heart Study in 2000.

Probability that an ego will become obese according to the type of relationship

Megacities of the world in 2015

What do we need more from modellers?

• Explore connections between disease dynamics and structural determinants

• Use more than one modelling approach per issue• Regularly validate past and present modelling• Engage with evaluation of complex health

interventions to generate counterfactuals against which to compare observed trends.