why the world needs vaccines for tb

Why the world needs

vaccines for TB

The Power of Vaccines: ‘getting to zero’ for HIV and TB TB-HIV Working Group

UK Consortium on AIDS and International Development

World AIDS Vaccine Day

May 18th 2012

Dr Richard White TB Centre

Centre for the Mathematical Modelling of Infectious Disease

Department of Infectious Disease Epidemiology

London School of Hygiene and Tropical Medicine

Richard.White@lshtm.ac.uk

Improving health worldwide

www.lshtm.ac.uk

Why the world needs

vaccines for TB

• Global TB burden

• Global TB control targets

• How are we doing?

• TB ‘Elimination’ - what do models have to say about how we might get there?

• Summary

Global TB burden (2010)

8.8

1.451.1

0.350.440.15

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

TB disease cases Deaths

Esti

mat

ed

nu

mb

er

case

s an

d

de

ath

s, M

illi

on

s

All forms TB

HIV associated TB

Multidrug resistant TB

WHO. Global tuberculosis control 2011. Geneva.

South-East Asia, 40%

Western Pacific, 19%

Africa, 26%

Eastern Mediterranean,

7%

Europe, 5%Americas, 5%

Global TB disease

incidence by region (2010)

• Highest burden in Asia – 59%

• Highest rates in Africa – About 80% of cases HIV infected

WHO. Global tuberculosis control 2011. Geneva.

Why the world needs

vaccines for TB

• Global TB burden

• Global TB control targets

• How are we doing?

• TB ‘Elimination’ - what do models have to say about how we might get there?

• Summary

Global TB control

targets

• UN Millennium Development Goals – 2015: … begun to reverse [rising TB] incidence

• Stop TB Partnership – 2015: 50% reduction in TB prevalence and deaths

– 2050: Elimination of TB ‘as a public health problem’ (<1 case per million people)

Why the world needs

vaccines for TB

• Global TB burden

• Global TB control targets

• How are we doing?

• TB ‘Elimination’ - what do models have to say about how we might get there?

• Summary

How are we doing?

Strategy

WHO (2006). The Stop TB Strategy, WHO / Stop TB. Geneva

How are we doing?

Progress in 2011

• 46 million people successfully treated (1995-2010)

• ~7 million lives saved compared to 1995 standard of care

• Millenium Development Goals (declining TB disease in 2015) – Peak in ~2002

– On track

• Stop TB (50% reduction in mortality between 1990 and 2015) – Reduced by 40% since 1990 in 2006

– On track

WHO. Global tuberculosis control 2011. Geneva.

How are we doing?

Global estimated TB disease incidence,

prevalence and mortality

WHO. Global tuberculosis control 2011. Geneva.

Target Target

40% decline since 1990

Currently ~1% annual decline

TB disease incidence TB disease prevalence TB mortality

But • TB disease incidence decline very slow • Case detection improvements slowing • MDR-TB care only now scaling up

Why the world needs

vaccines for TB

• Global TB burden

• Global TB control targets

• How are we doing?

• TB ‘Elimination’ - what do models have to say about how we might get there?

• Summary

What can we achieve with the

existing strategy?

Lonnroth et al, Social Science and Medicine, 2009

Current decline (1%/yr)

Decline required for ‘Elimination’ (16%/yr)

Predicted decline with full implementation of Global Plan to Stop TB (6%/yr)

‘Elimination’ by 2050

What would it take?

• Impact of treating active TB disease cases OR using new pre-exposure vaccine large

• But impact limited as neither directly prevents reactivation disease among latents (1 in 3 people worldwide)

• ‘Elimination’ unlikely • Elimination more likely if • Combination prevention

approach used that a) Prevents reactivation

disease among latents using preventative drug therapy OR a post-exposure vaccination

AND b) Prevents/treats active

disease using a new pre exposure vaccination OR drug therapy

Dye et al, J R Soc Interface, 2008

‘Elimination’

Potential impact of new TB diagnostics,

drugs and vaccines on TB disease

incidence in SE Asia in 2050

Diagnostics

Drugs

Vaccines

Abu-Raddad et al, Proc Natl Acad Sci, 2009

• Dipstick point of care test

• 42% ↓ in TB incidence

• 2 month active disease therapy (including M/XDR) & mass latent therapy

• 94% ↓ in TB incidence

• Mass pre and post exposure vaccines

• 92% ↓ in TB incidence

) at microscopy lab level

point of care test

Active disease #1: 4 month, no MDR effect Active disease #2: 2 month, 90% MDR effect Active disease #3: 10-day, 90% MDR effect

+ latency & case infectiousness effect

Dis

ease

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/mill

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) D

isea

se in

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ence

(/m

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n)

Dis

ease

inci

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ce (

/mill

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)

Why the world needs

vaccines for TB

• We should meet the (rather underwhelming) target of slow annual reduction in global TB disease incidence in 2015

• Using current tools we are unlikely to get close to eliminating TB disease as a public health problem by 2050

• Can get closer to elimination using combination-prevention strategies that prevent/treat active disease AND prevent disease due to reactivation of latent infection

• But, to do so we would need strategies like – mass treatment of latent MTB infection OR new post-exposure vaccine AND – high coverage of effective disease therapy OR new pre-exposure vaccine

• Of these DOTS coverage increase has stalled, and mass treatment of latent MTB infection is difficult to scale up

=> New vaccines, drugs and diagnostics are required

Improving health worldwide

www.lshtm.ac.uk

Why the world needs

vaccines for TB

Dr Richard White TB Centre

Centre for the Mathematical Modelling of Infectious Disease

Department of Infectious Disease Epidemiology

London School of Hygiene and Tropical Medicine

Richard.White@lshtm.ac.uk

Improving health worldwide

www.lshtm.ac.uk