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Volume 15, Number 8—August 2009

Past, Present, and Future of Japanese Encephalitis

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To the Editor: We are writing in response to the perspective on Japanese encephalitis (JE) by Erlanger et al. (1). Growing awareness is encouraging, yet because JE is a largely neglected disease, information is often contradictory or not readily available. We would like to supplement the authors’ review with clarification on available vaccines and actions countries are taking to evaluate and control JE.

There is room for improvement or expansion on collecting and reporting JE surveillance data. However, as vaccine availability increases, many countries are eager to determine the impact of JE and to make informed decisions on immunization programs. For example, surveillance in Indonesia from 2005 through 2006 confirmed human cases throughout the country (2). In Cambodia, JE surveillance commenced in 2006, and an immunization program is being planned (2). Regional JE laboratory networks established by the World Health Organization are also helping countries gather this information by strengthening diagnostic capacity.

Cambodia plans to introduce the live, attenuated SA 14-14-2 vaccine from China’s Chengdu Institute of Biological Products. This vaccine has recently become internationally available and is increasingly replacing the inactivated, mouse brain–derived vaccine in Asia. A single dose of the SA 14-14-2 vaccine demonstrated 96% efficacy after 5 years (3), and the Institute’s commitment to an affordable price for developing countries has broadened accessibility (4). The government of India introduced the SA 14-14-2 vaccine in 2006, and nearly 50 million children 1–15 years of age have been reached through vaccination campaigns and routine immunization. The vaccine also is available through public programs or private markets in China, Nepal, South Korea, Sri Lanka, and Thailand.

JE vaccine candidates in late-stage development for children include a live, attenuated chimeric virus vaccine and an inactivated, Vero cell–derived vaccine, each based on the SA 14-14-2 virus strain. Additionally, 2 inactivated, Vero–cell derived vaccines based on the Beijing-1 strain are being developed in Japan (5).

New vaccine development, along with progress in surveillance and immunization, offers promise for sustainable control of clinical JE. To achieve this, global partners are working together to develop a strategic plan for JE control by 2015 (6).


Susan L. HillsComments to Author  and Deborah C. Phillips
Author affiliations: PATH, Seattle, WA, USA



  1. Erlanger  TE, Weiss  S, Keiser  J, Utzinger  J, Wiedenmayer  K. Past, present, and future of Japanese encephalitis. Emerg Infect Dis. 2009;15:17. DOIPubMedGoogle Scholar
  2. World Health Organization. Third Biregional Meeting on Control of Japanese Encephalitis; 2007 Apr 26–27; Ho Chi Minh City, Vietnam. Manila: World Health Organization Regional Office for the Western Pacific; 2007 [cited 2009 Jan 15]. Available from
  3. Tandan  JB, Ohrr  H, Sohn  YM, Yoksan  S, Ji  M, Nam  CM, Single dose of SA 14-14-2 vaccine provides long-term protection against Japanese encephalitis: a case–control study in Nepalese children 5 years after immunization. Vaccine. 2007;25:50415. DOIPubMedGoogle Scholar
  4. World Health Organization. Sixteenth Meeting of the Technical Advisory Group on Immunization and Vaccine Preventable Diseases in the Western Pacific Region; 2006 Jun 20–22; Manila, Philippines. Manila: World Health Organization Regional Office for the Western Pacific; 2006 [cited 2009 Jan 15]. Available from
  5. Beasley  DWC, Lewthwaite  P, Solomon  T. Current use and development of vaccines for Japanese encephalitis. Expert Opin Biol Ther. 2008;8:95106. DOIPubMedGoogle Scholar
  6. Elias  C, Okwo-Bele  J, Fischer  M. A strategic plan for Japanese encephalitis control by 2015. Lancet Infect Dis. 2009;9:7. DOIPubMedGoogle Scholar


Cite This Article

DOI: 10.3201/eid1508.090149

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Susan L. Hills, PATH, 1455 NW Leary Way, Seattle, WA 98107, USA;

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Page created: September 30, 2010
Page updated: September 30, 2010
Page reviewed: September 30, 2010
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.