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.

Japanese Encephalitis:Control of the Disease

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.

JE transmission cycle and possible control points

Control options

• Mosquito control?

• Pig control?

• Human interventions?

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

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

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

 

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

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

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.

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

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

JE vaccine: what are the options?

JE vaccines currently available fall into 2 categories

• Inactivated vaccines

• Live, attenuated vaccine

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.

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.

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:

• 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)

• 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

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.

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