How PATH and our partners assess impact against a life-threatening disease

What we did

We helped countries in Asia and the Pacific monitor and understand the extent and impact of Japanese encephalitis (JE) and introduce a safe, affordable vaccine.

Why we chose to work on Japanese encephalitis

Approximately 3 billion people—including 700 million children—live in areas at risk for Japanese encephalitis. Up to 50,000 cases are reported annually. The World Health Organization (WHO) estimates that JE claims 10,000 to 15,000 lives a year. Because awareness of JE is low and the disease is difficult to diagnose, these figures may significantly underestimate JE’s impact.

Even less recognized is the lifelong toll that JE takes on its survivors. Up to half of survivors suffer neurological damage that will affect them for the rest of their lives. Among survivors, half to three-quarters will have long-term disabilities, including intellectual, behavioral, or neurological disabilities like paralysis or the inability to speak.

There is no cure for JE.

Our goal

Eliminate clinical JE and avoid unnecessary death and disability caused by the disease.

Our strategy

The only way to effectively control JE is through vaccinating people against it.

The impact of JE vaccination is illustrated by the difference between the number of Japanese encephalitis cases before and after the start of immunization programs. As Figures 1 and 2 show, the annual number of JE cases in both Japan and Thailand dropped dramatically—in Japan’s case to zero—in the years after immunization began in those countries.

Figure 1. Evolution of JE control in Thailand

Source: Ministry of Health, Thailand, 1998.

Figure 2. Annual number of JE cases in Japan, 1948 to 1998

Source: Igarashi A. Control of Japanese encephalitis in Japan: immunization of humans and animals, and vector control. Current Topics Microbiology and  Immunology. 2002;267:139–52.

Results: improved data for decision-making

PATH collaborated with national governments as well as with WHO and UNICEF to establish sustainable systems for diagnosing JE, tracking its incidence, and modeling the cost-effectiveness of introducing vaccine. These actions provided policymakers with the information they needed to make decisions on JE control.

The accuracy and usability of tests used to diagnose JE have been a barrier to identifying cases of the disease—and determining its impact on populations. PATH and our partners conducted studies to evaluate the tests and helped private-sector partners develop standard versions. We worked with WHO and governments to set up surveillance systems to track JE and a web-based platform for sharing data about its incidence. Accurate diagnosis and surveillance data helped policymakers see the extent of JE in their countries, prioritize it, and focus prevention efforts on the regions and people that most needed protection.

To make delivery of JE vaccine simpler and more cost-effective, we conducted a clinical trial to help determine whether children can safely receive a live JE vaccine along with routine measles vaccination. After reviewing the data, WHO’s Global Advisory Committee on Vaccine Safety concluded that the short-term safety profile of live JE vaccine given with measles vaccine was acceptable.

Results: advance availability of an improved, cost-effective vaccine

When our project started, the most commonly used JE vaccine was expensive, hard to produce, and often unavailable. Looking for an alternative, we identified another effective vaccine that had been safely used in China for more than 20 years. Because the vaccine had not been used widely outside of China, international officials called for specific clinical studies. Collaborating with the manufacturer, WHO, and ministries of health, PATH conducted pivotal clinical trials to add to a growing collection of data on the vaccine.

To help support the vaccine through the essential WHO prequalification process, PATH is providing support and technical assistance for construction of a new manufacturing facility. The new facility will help the vaccine’s manufacturer meet demand and reach international standards for good manufacturing practices. Working with PATH, the manufacturer has agreed to price breaks for the public sector to enable access in poor countries.

Results: introduction and integration of the vaccine

PATH and our partners provided technical assistance to countries using the JE vaccine—from developing strategy to  implementing and evaluating immunization programs. Results of our efforts include:

• Some 60 million children vaccinated against JE in India. India’s five-year strategy is to reach 100 million children ages 1 to 15 years in high-risk districts, then introduce routine JE immunization.
• A commitment to a sustained immunization effort for children and adults in Nepal.
• Transition from the older, more expensive vaccine to the newer, less costly vaccine in Sri Lanka. Cost savings will allow for program sustainability, budget for other new vaccines, expansion of childhood JE immunization nationwide, targeting of vulnerable adults in high-risk areas, and the potential to add a second dose of JE vaccine, if necessary.
• Vaccination of about 1.5 million children in the Democratic People’s Republic of Korea through collaboration with the Ministry of Health and other organizations.
• Introduction of JE vaccine in Cambodia on a small scale in October 2009.
• Plans to expand JE immunization program nationwide in Vietnam.

Results: expanded outreach through advocacy

Throughout the project, we shared information to raise awareness of JE at global, national, and regional levels. Our advocacy efforts helped make JE immunization a priority, foster collaboration, and inform strategies for its control. The materials we developed include training presentations, three short films, Q&As, and peer-reviewed publications.

The bottom line

By analyzing surveillance data in countries that have introduced the new JE vaccine, over time we will likely see the benefits of this work in lives saved and disabilities avoided. A recent study in India showed that children who had been vaccinated were about one-fifth as likely to get JE as children who had not been vaccinated, equivalent to an 80 percent reduction in disease after vaccination. As children receive vaccine, cases of JE are likely to drop, as they have in Thailand, Japan, and other countries (see figures 1 and 2). With fewer cases of JE will come fewer deaths and disabilities attributable to the disease. We will continue to monitor data in order to further assess the impact of the project.

Illustrations: PATH.