What It Is and What It Protects Against 

Japanese encephalitis is a virus that is transmitted through the bite of infected mosquitoes most commonly in rice fields and other rural areas. It is closely related to the St. Louis and West Nile viruses that cause acute inflammation of the brain and spinal column. Symptoms of infection begin with fever and headache, but can develop into high fever, disorientation, tremors, stiff neck, convulsions, and paralysis.  The virus causes between 10,000 to 15,000 deaths annually in Asia. Infection is most common in children as adults tend to build up a tolerance to the virus through prior infection.

A vaccination against Japanese encephalitis is manufactured under the brand name Ixiaro. It is an inactive immunization that comes in ready-to-use prefilled syringes. Two doses are give 28 days apart to people 17 years and older. Clinical trials are currently underway to test the vaccination’s safety against people under the age of 17.

General Use

Adults traveling to Asia are strongly encouraged to get the vaccination. Unlike local people, travelers will most likely not be exposed to the virus and not built up immunities to the virus.

The two doses of Ixiaro should be administered a week before potential exposure to the virus.

Who Should Not Get It

Children under the age of 17 should not get the vaccination, as it has not been approved for use in children.

Ixiaro contains protamine sulfate, which can cause allergic reactions in some people. If you’re allergic to protamine sulfate, you shouldn’t get the vaccination.

Potential Side Effects

The most common side effect of the vaccination is pain and tenderness at the injection site. Less than ten percent of people in clinical trials for Ixiaro experienced headache and muscle pain.

In the same trials, more than half of test subjects had some kind of adverse reaction. The serious reactions, which were less than one-half of 1 percent experienced, appendicitis, rectal hemorrhaging, chest pain, ruptured cysts of the ovaries, and other problems.