Japanese encephalitis vaccine support

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Spread by mosquitos, Japanese encephalitis is the main cause of viral encephalitis in Asia

Case-fatality rates are estimated at 20–30%, while up to 30% of survivors suffer permanent disability

Rice paddies, prevalent throughout Southeast Asia, are breeding grounds for mosquitos that carry the Japanese encephalitis virus.

Rice paddies, prevalent throughout Southeast Asia, may make for a beautiful landscape, but they are also optimal breeding grounds for mosquitos that carry the JE virus. Photo: PATH/2013

Outside of Asia, Japanese encephalitis (JE) is relatively unknown, but some three billion people live in areas at risk of the viral disease. JE is especially prominent in the poor rural communities of eight Gavi-eligible countries in South-East Asia and the Western Pacific.

The disease

Often called “brain fever”, JE begins with flu symptoms, progresses to a brain infection and claims the lives of 20–30% of infected infants and children. According to the World Health Organization (WHO), annual mortality is estimated at 13,600 to 20,400 deaths each year. However, awareness of the disease is low and the figures may underestimate the real impact. In 2005, a devastating outbreak of JE killed nearly 2,000 people in India and Nepal, mostly children.

JE’s lifelong toll on its survivors is even less known. In the most severe cases, an estimated 30% of cases result in permanent neurological weaknesses, with an even higher rate reported in children.


The virus is hosted by wading birds like herons and egrets, which flock to rice paddy fields, and by the pigs commonly raised in rural areas. It’s then transmitted to humans by mosquitoes.

JE cannot be transmitted from one person to another.


There is no specific treatment for JE. Prevention of the disease through effective and relatively inexpensive vaccines is the best control strategy.

Some Gavi-eligible countries have already initiated JE vaccination programmes, either routine or campaigns. Gavi support allows countries to reach children aged between 9 months and 14 years through catch-up campaigns.

Burden of disease

The disease is endemic with seasonal distribution in parts of China, the Russian Federation’s south-east and South and South-East Asia. All year transmission is observed in tropical climate zones.

Risk factors for JE include living in close proximity to pigs and to irrigated rice fields.

Lao PDR became the first country to conduct a JE campaign with Gavi support in 2015

Students in Vientiane, Lao People’s Democratic Republic, after receiving their first dose of Japanese encephalitis vaccine.

Students in Vientiane, Lao People’s Democratic Republic (PDR), after receiving their first dose of Japanese encephalitis (JE) vaccine. In 2015, Lao PDR became the first country to use support from Gavi to protect its children from JE. Photo: Bart Verweij

In 2014, Gavi invited countries to apply for support to introduce the Japanese encephalitis (JE) vaccine. The first Gavi-funded JE vaccine campaigns started in Lao People’s Democratic Republic in 2015, with Nepal and Cambodia scheduled for 2016.

In line with WHO recommendations, Gavi is providing support for JE catch-up campaigns on the basis that countries self-finance the introduction of the vaccine in their routine immunisation programmes.

The campaigns target children aged 9 months to 15 years and ensure sustainability by embedding JE vaccine into routine immunisation programmes. This catalytic support will have a sustainable and positive impact on JE control efforts.


In 2011, the Gavi Board recommended opening a window for country applications for Gavi support, pending the prequalification of an appropriate JE vaccine.

In October 2013, WHO added a JE vaccine, known as SA 14-14-2 and developed by China’s Chengdu Institute of Biological Products, to its list of prequalified vaccines – opening the door for United Nations agencies to procure the vaccine. It is the first Chinese-produced vaccine to be prequalified by WHO, and the first prequalified JE vaccine for paediatric use.

Recognising JE’s burden of disease, PATH has collaborated with the Chengdu Institute, WHO and ministries of health on clinic trials to demonstrate that the vaccine, made from an active but weakened virus, is both safe and effective. It also only requires one dose.

PATH also negotiated with the manufacturer to ensure a special public-sector price affordable for low-income and some middle-income countries at risk of JE transmission, such as the Philippines.

WHO recommends immunisation in all regions where the disease is a recognised public health problem. Additional prequalified vaccines appropriate for paediatric use are expected to be prequalified in the near future, adding to the choices available for countries.

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