About Japanese Encephalitis

Japanese encephalitis (JE) is a mosquito-borne acute arbovirus infection of the nerve center system in human being and animals.

Japanese encephalitis virus (JEV), a member of the family Flaviviridae, genus Flavivirus, is a single-stranded, positive-sense RNA virus. It is spherical, and 40-50nm in diameter. Japanese encephalitis virus has strong endurance of low temperature and can survive of xeransis environments.

JE is a significant public health problem in southeast Asia and western Pacific areas. The prevalence of JE in , Philippine, , , , , is associated with either local climate or activities of mosquitoes that carry virus. In China，the transmission of JE is usually seasonal , occurring in summer and autumn-mainly July to September. Mosquitoes, having bitten the infected people or animals, are the contagion resources transferring the JE virus to health people by biting them. It is considered that pigs and mosquitoes are hosts of deposition and transmission of the virus, respectively. The incubation period of JE is 10 to 14 days. JE is clinically specialized by clearly seasonal outbreak, emergent occurrence, hyperpyrexia, headache and unconsciousness. The course of disease is about two weeks and it can result in death within one week after infection. JE has a high mortality of about 30%. In the endemic areas, 85% cases are children under 15 years old, and those under 10 years old are liable to bear serious neurological and psychiatric sequelae, such as alogia, paralysis, anoia, dementia, malformation of limbs, convulsion, and so on.


At present, there is no JE-specific therapy other than supportive care to control the development of the disease in hospital. Human, especially children, are susceptible to JEV.

Therefore, it is very important to prevent children from JE infection.

Why develop this vaccine?

Inactivated mouse brain-derived JE vaccines have been available internationally for many years. The main manufacturer is Biken, . There are also several JE vaccines manufactured in china, including inactivated mouse brain-derived vaccine, inactivated hamster kidney cell-derived vaccines, live-attenuated hamster kidney cell-derived vaccines and Vero cell-derived inactivated JE vaccine.

Inactivated mouse brain-derived vaccine and Inactivated hamster kidney cell-derived vaccine require multiple inoculations because of their weak immunogenicity. And they may introduce animal tissue-derived foreign substances into vaccinees’ bodies, which is the most important reason for causing allergic reactions. Live-attenuated Vaccine can decrease these reactions with less inoculation times, but it is reported that the vaccine may result in death of the animals bearing immunity system deficiency as the virus of the vaccine may proliferate in them, which indicates that the vaccination of live-attenuated vaccine to those of immunity system deficiency may bring about safety problems. In addition, live-attenuated vaccine hasn’t been approved by WHO for it neither uses the cells of SPF animals nor removes the contamination of foreign substance. An inactivated vero cell-derived lyophilized JE vaccine has been available in china. It is safe and effective without the defects mentioned above, and it can meet the international requirements. However, at present there is only one company who produces vero cell-derived inactivated JE vaccine and it adopt traditional rotate-bottle cultivate technology, therefore the output is low and could not satisfy the demand of domestic and international market for its low output using.

The new inactivated JE vaccine we are developing, using the microcarrier technology for cultivating of virus, will be more safe and effective for preventing JE. Vero cell has been authorized by WHO as host cell to produce vaccine. Since JE has been included in planning immunization in china from 2005, it will occupy the domestic market as well as supply to satisfy the demand of the international market once the project succeeds .