Japanese encephalitis (JE)
Introduction
Japanese encephalitis (JE) is the leading cause of viral encephalitis throughout large parts of Asia. The disease, which is transmitted by Culex mosquitoes, is endemic in most parts of Asia with temperate and subtropical or tropical climate. The disease affects mostly infants and children, but all age groups can develop the disease. There is underreporting of cases, and conservative figures estimate some 50,000 cases annually, with a 25-30% mortality rate and 30% rate of long-term sequelae among survivors. There is no treatment for the disease available, making vaccination a public health priority for endemic countries.
Inactivated JE vaccines have been available since several decades and have shown their capacity to control the disease in countries where they have been used programmatically. However, despite their proven efficacy, overall utilization of these vaccines have remained low, which is primarily due to their relatively high cost and the need for multiple doses and booster immunizations. Moreover, lack of reliable disease-burden data has contributed to low prioritization of JE vaccination.
Together with partners, in particular the JE Program at PATH, WHO has developed a comprehensive agenda to support JE vaccination. Activities build on the promising pipeline of new and improved JE vaccines that will soon become available, and include epidemiologic studies and programmatic planning in relation to immunization, and regulatory, normative and research activities in support of new JE vaccines. Financing mechanisms need to be put in place to assure access to these much-needed vaccines.