Japanese Encephalitis (JE) is a serious illness that affects the brain. When persons get clinical disease 1/3rd will recover from the disease, 1/3rd will die and 1/3rd will have neurological deficits meaning they will have some kind of serious brain damage. The virus that causes JE is carried by culex mosquitoes which breed in flooded rice fields. Mosquitoes feed on infected pigs and wild birds and infected mosquitoes transmit JE virus to humans and animals while feeding. Since human infection is incidental, there is no person to person transmission. The disease is inherently rural in nature. JE is endemic in the Terai (southern Nepal that borders with India) with maximum number of cases occurring in the western districts of Banke, Kanchanpur and Kailali. An immunization program targeting children in the affected districts has decreased the number of cases in the Terai. The highest risk months for JE are August, September and early October of each year. JE was first confirmed in the Kathmandu valley in 1996 and cases occur each year in these high risk months.  

This raises the question as to whether all residents and tourists to Kathmandu valley should receive the vaccine against JE.

Short term travelers who will stay in Kathmandu for less than a month who will go trekking are the lowest risk individuals and we do not feel that they need to be immunized against JE. Travelers who will reside in Kathmandu for more than a month particularly in the post-monsoon months of August to October are recommended to obtain the JE vaccine. Persons who will be living in known JE endemic areas such as most of the Terai and those who live in Kathmandu particularly in the rural areas of the valley should be immunized against JE.

The JE vaccine that we stock (Biken vaccine) is manufactured in Japan, and consists of three shots over a one month period. There is a rapid schedule over a 2 week period for individuals with time constraints. Production of this vaccine was phased out in 2005 and we are currently using left over stock of this vaccine. New vero cell vaccines are expected to be available in 2009. Although Biken vaccine is generally a safe vaccine, local and systemic side effects can occur. Side effects can occur for up to 10 days after receiving the vaccine. For this reason, we recommend that you avoid travel to remote places for 10 days after receiving the vaccine.

A live attenuated vaccine consisting of the SA14-14-2 strain produced by Chengdu Institute in China has been available in Nepal since 1999. It is a very safe vaccine with no serious side effects like encephalitis or hypersensitivity reactions reported in over 200 million doses used in Asia. Single shot seems to offer protection for up to 5 years with booster every 5 years. In children, manufacturers recommend 2 shots one year apart when started at age 9months-1 year. We are starting to stock and use this vaccine at the CIWEC Clinic although we still have a few doses of the Biken vaccine remaining.   

Since JE is transmitted by the bite of an infected mosquito, mosquito bite prevention measures are just as important to protect against this disease.

(Revised: August 2008)