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Ad-hoc group of experts on cholera vaccines 28 October 2009
Dominique Legros, MD MPH
WHO
Cholera Vaccine use: The public health perspective
Strategic Advisory Group of Experts on Immunization
28 October, 2009
Ad-hoc group of experts on cholera vaccines 28 October 2009
Introduction
Improvements in sanitation and access to clean water – The mainstays of preventing endemic and epidemic cholera – "Sanitary revolution" of the 19th century – Situation in least developed countries today
Methods of prevention and control of cholera – Preventing / reducing spread of the disease – Reducing mortality
Limitations of current methods
Vaccination with oral cholera vaccines as an additional public health tool to reduce the risk of infection
Ad-hoc group of experts on cholera vaccines 28 October 2009
Cholera prevention and control - reducing mortality
Early case detection
Increase access to health care (treat cases promptly)
Adequate patients care – Adapted health care infrastructures (decentralised, separate
cholera patients) – ORS and IV fluids – Antibiotics – Feeding practices
Ad-hoc group of experts on cholera vaccines 28 October 2009
Cholera prevention and control - Preventing / reducing spread
Early detection of epidemics
Safe water : piped water system, water treatment, safe water storage and use
Excreta disposal : latrines and sewerage systems, culturally acceptable, affordable, easy to maintain
Hand washing with soap
Safe food
Health Education / Social mobilization for behaviour change
Infection control practices
Ad-hoc group of experts on cholera vaccines 28 October 2009
Limitations of prevention and control methods
Cholera often affects the poorest of the poor – Access to those groups (geographical, security, cultural, etc.) – Reduced access to health care
Quality of health care in areas regularly affected by outbreaks or endemic
– Investment in health system
Access to ORS
Resistance to antibiotics
Ad-hoc group of experts on cholera vaccines 28 October 2009
Large outbreaks and scale of the intervention – Burden on health care system – Heavy water & sanitation interventions (i.e. water trucking)
Investments to built sewerage or piped water systems
Changing behaviours – Difficulty – Sustainability
Limitations of prevention and control methods (2)
Ad-hoc group of experts on cholera vaccines 28 October 2009
Vaccination with oral cholera vaccines
As an additional strategy for endemic and epidemic cholera situations to reduce the risk of infection
Synergistic with water and sanitation interventions
Ad-hoc group of experts on cholera vaccines 28 October 2009
Current WHO recommendations for the use of Cholera Vaccines
The use of OCV should be recommended in "certain endemic situations"
The use of OCV should be complementary to existing strategies for cholera control and, in complex emergencies, should not interfere with "other critical public health interventions"
Vaccination with the current internationally available prequalified vaccine (2005) is not recommended once a cholera outbreak has started
Demonstration projects using oral cholera vaccines should be implemented
Ad-hoc group of experts on cholera vaccines 28 October 2009
DUKORAL®: Feasibility of Mass Vaccination Campaigns
Location # of Doses
Uganda1 1997 63,220
Mayotte 2000 93,000
Mozambique2 2003/04 82,000
Darfur3 2004 103,000
Indonesia 2004 137,000
Zanzibar 2009 100,000
1 Legros D, et al. Bull World Health Organ 1999;77:837-42. 2 Lucas M et. al. N Engl J Med 2005; 352: 757-67. 3 WHO. Darfur Disease Outbreak control Bulletin. 2004 Aug 15. Available at: www.who.int/disasters/repo/14372.pdf.
Ad-hoc group of experts on cholera vaccines 28 October 2009
Demonstration project in a highly endemic setting in Africa, Mozambique, 2003/04
• Partnership: MOH; MSF/Epicentre; IVI; WHO
• Killed WC-rBS oral cholera vaccine (2 doses)
• 44,878 people vaccinated
• Vaccine coverage of the target population was 53.6% (after 2nd dose)
• Mass vaccination campaign before the season was feasible and acceptable
• Vaccine effectiveness 78%
Cavailler et al. Vaccine 2006 and Lucas M et al. NEJM 2005
Ad-hoc group of experts on cholera vaccines 28 October 2009
Field experience in Zanzibar, 2009
Target population 50,000 subjects (>2 yrs) – 100,000 doses provided – 1st round – 11-26 January 2009 (9 outposts) – Inter-round interval of 12 days – 2nd round – 7-16 February 2009 (9 outposts)
Mass cholera vaccination – Feasible and well accepted – In the short-term: scale-up vaccination
throughout Zanzibar
Ad-hoc group of experts on cholera vaccines 28 October 2009
Pre-emtive vaccination in complex humanitarian emergencies, Kalma camps, Darfur, Sudan
● 53,537 internally displaced persons (IDP's) in 2 camps
● 103,000 doses provided of the killed WC-rBS oral cholera vaccine (2 doses)
● Estimated vaccine coverage 88% ● 42,878 received 1 st dose ● 40,388 received 2nd dose. ● 13,400 vaccinated in one day
WHO. Darfur Disease Outbreak control Bulletin. 2004 Aug 15. Available at: www.who.int/disasters/repo/14372.pdf.
Ad-hoc group of experts on cholera vaccines 28 October 2009
OCV - Recent developments and their Public Health consequences
Well accepted by the populations in both endemic and epidemic settings
Herd protection to non-vaccinated individuals
No buffer for administration – Reduced logistic constraints – More flexible vaccination strategies
Reasonable price – Increased access for countries
Ad-hoc group of experts on cholera vaccines 28 October 2009
Vaccination Strategies
Vaccination strategy to be adapted to each context – Based on the epidemiological pattern of cholera, the capacity of
the immunization program and health system, the capacity to organize a mass campaign, the specific economic and cultural conditions, etc.
In endemic situations – Universal vaccination throughout the country is probably not
warranted in most places – Periodic mass vaccination campaigns targeted at high risk
populations / regions are the most practical option – Re- vaccination may be required every 2 years
Ad-hoc group of experts on cholera vaccines 28 October 2009
Vaccination Strategies
In outbreak situations – Pre-emptive vaccination targeting populations with limited access
to safe water or sanitation – Reactive vaccination in areas not yet affected during large
outbreaks – Investigation of the current and historical epidemiological situation
and identification of areas/populations to be targeted – Treatment of cases, water and sanitation interventions, and
community mobilization : the mainstays of control measures
Ad-hoc group of experts on cholera vaccines 28 October 2009
Summary
Public Health prevention and control measures of cholera well known since decades but with limitations
Vaccination with oral cholera vaccine as an additional prevention strategy for endemic and epidemic cholera situations
Recent OCV developments should facilitate their use as a public health tool with adapted vaccination strategies