japanese encephalitis: control of the disease
TRANSCRIPT
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Instructions for users• This slide presentation provides an overview of
the control of JE and prevention of JE by immunization.
• Below many of the slides, there are notes to explain the information in the slide.
• You should adapt the presentation for your own use.
• If you want to present this topic in a more in-depth way, resources are suggested in the notes section below.
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Japanese Encephalitis:Control of the Disease
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Learning Objectives
Participants will:
• Understand methods that have been used to try to control JE and problems with them.
• Understand the importance of human immunization for JE.
• Be familiar with the scientific evidence for effectiveness and cost-effectiveness of JE immunization.
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JE transmission cycle and possible control points
Control options
• Mosquito control?
• Pig control?
• Human interventions?
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Mosquito control ?
• Spraying mosquito habitats with insecticide — Time consuming, expensive, it
is difficult to cover all mosquito habitats, and causes environmental pollution
• Bednets— Mosquitoes often bite at dusk
before people are in bed
NOT THE BEST SOLUTIONPhoto credit: Julie Jacobson
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Pig control ?
• Segregating, slaughtering, or vaccinating pigs
— Economically not feasible and difficult
— Other animals, like birds, may also act as amplifying hosts so even if pigs are eliminated JE will not disappear
NOT THE BEST SOLUTIONPhoto credit: Susan Hills
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Conclusion:
“Human vaccination is the only effective long-term control measure against JE. All at-risk residents should receive a safe and efficacious vaccine as part of their national immunization program.”
Consensus statements from Global JE meetings
1995, 1998, and 2002
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World Health Organization statement:
“where affordable, JE vaccination should be extended to all endemic areas where JE is considered a public health problem”
WHO, 1998Weekly Epidemiological Record No. 44
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Scientific evidence for JE immunizationThere is compelling evidence that human immunization is effective for controlling JE. Studies in Korea and Japan showed >99% reduction in JE cases after immunization.
Source: Igarashi A. “Control of Japanese Encephalitis in Japan: Immunization of humans and animals and vector control” Current Topics in Microbiology and Immunology 2002. 267: 139-152
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JE immunization is cost-effective
• Studies in several countries have shown JE immunization to be cost-effective.
• A study in China showed JE immunization to be cost-saving (i.e., the costs of procuring and delivering the vaccine were less than the economic costs of treating the disease in the absence of immunization).
• This suggests that investing in immunization against JE can actually save resources.
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Cost-effectiveness of vaccination – the China study*• The study examined a hypothetical birth cohort of 100,000
persons from Shanghai.
• Compared the use of live & inactivated vaccine to no vaccine.
• With inactivated vaccine: prevented 420 cases and 105 deaths per 100,000 vaccinees.
• Live vaccine: prevented 427 cases and 107 deaths.
• Both vaccines cost-saving.
• Live vaccine strategy had greater cost savings compared to inactivated vaccine strategy.
* Ding D et al. Bull WHO 2003;81(5):334-42
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Status of JE control with immunization
Comprehensive immunization program:
Japan, South Korea, Taiwan and Thailand
Program commenced and plans for expansion or development
China, India, Nepal, Sri Lanka, Vietnam
Limited immunization program:
Malaysia
Data as of October 2006
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JE vaccine: what are the options?
JE vaccines currently available fall into 2 categories
• Inactivated vaccines
• Live, attenuated vaccine
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Inactivated mouse brain-derived JE vaccine
• First licensed in Japan in 1954.
• The most widely used and available vaccine.
• Has been produced by several countries, including Japan, S. Korea, Thailand, and Vietnam.
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Live, attenuated JE vaccine (SA 14-14-2 vaccine)
• First licensed in China in 1988.
• Used extensively in China.
• Also licensed in Nepal, India, South Korea and Thailand.
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Comparison of the vaccines
• Simpler schedule
• Better safety profile
• Longer duration of action
• Cheaper price
The benefits of the live attenuated vaccine compared to the inactivated vaccine are as follows:
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• No JE vaccine has been pre-qualified by WHO at this time (September 2008). However WHO endorses use of JE vaccine in controlling JE.
• There are supply problems with the inactivated vaccine; it is no longer being produced in Japan, the major manufacturer, and supply is insufficient for global need.
Comparison of the vaccines (2)
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• Inactivated Vero-cell derived vaccine (SA 14-14-2 viral strain)
• Vaccine for adults submitted for licensure in US
• Pediatric clinical trials commenced in India in 2007
• ChimeriVax™-JE live recombinant vaccine
• Vaccine for adults in advanced stage of development
• Pediatric clinical trials commenced in India in 2007
• Inactivated Vero cell-derived vaccine (Beijing virus strain)
• Pediatric clinical trials in progress in Japan
New vaccines in development
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Control of JE by vaccination: summary• Vaccine supply problems, cost, scheduling
difficulties and other issues have resulted in slow progress of implementation of JE immunization in some countries.
• However, many countries are making good progress towards control of JE by immunization.
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Acknowledgements
Please include the following acknowledgement if you use this slide set:
This slide set was adapted from a slide set prepared by PATH’s Japanese Encephalitis Project.
For information: www.JEproject.org