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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.