Who Needs a Japanese Encephalitis Vaccine?

Mary McMahon
Mary McMahon
A small syringe and vaccine vial.
A small syringe and vaccine vial.

Japanese encephalitis vaccines are recommended for residents of areas where this virus is endemic, as well as for travelers who will be spending a month or more in a region when seasonal cases of the condition are high, and laboratory workers who handle the virus in lab settings. People who are preparing to travel to Southeast and East Asia should meet with their physicians to discuss whether they need a Japanese encephalitis vaccine, and should make sure they get their vaccinations at least 10 days before traveling to give the vaccine time to take effect. There are some groups of people for whom vaccination is contraindicated, including people with a history of allergic reactions to vaccines.

The Japanese encephalitis virus is spread by mosquitoes.
The Japanese encephalitis virus is spread by mosquitoes.

Japanese encephalitis is a form of viral encephalitis caused by being bitten by a mosquito carrying the virus. It cannot be passed directly between humans, and lives in animal hosts like pigs. In regions of Asia where populations of pigs are high, at certain times of the year, Japanese encephalitis infections can be common. Mild cases will result in a low fever, while more severe cases can cause neck stiffness, high fever, headaches, stiffness, and confusion. Some patients fall into a coma as a result of damage to the brain.

Travelers who will be in Japan for one month or longer should have a vaccination for Japanese encephalitis.
Travelers who will be in Japan for one month or longer should have a vaccination for Japanese encephalitis.

The Japanese encephalitis vaccine reduces the risk of getting the disease, but it doesn't completely eliminate chances of infection. People who have been vaccinated should still observe precautions like sleeping under mosquito nets and using insect repellents to keep mosquitoes away. People who notice symptoms of infection should seek treatment, and it is important to be aware of the up-to-two-week incubation period; someone who feels ill after returning home from traveling, for example, may have Japanese encephalitis.

The Japanese encephalitis vaccine offers some -- but not complete -- protection against the disease.
The Japanese encephalitis vaccine offers some -- but not complete -- protection against the disease.

Among travelers, people who will be spending a month or more in an area where the virus is common, or who are not sure about their itineraries, should receive a Japanese encephalitis vaccine if they are traveling at a time of year when rates are high in a given area. A travel doctor can provide more information and help people decide whether vaccination is advisable. Generally, children under one year of age should not be vaccinated, and the use of the vaccine is not recommended for pregnant and breastfeeding women, as the risks for them are not known.

People who have reacted badly to vaccines in the past should discuss this with a physician to see if the Japanese encephalitis vaccine contains ingredients that could be dangerous for them. It contains ingredients derived from rodents, as well as neural cells, and these can also potentially cause reactions.

Residents of areas with Japanese encephalitis should get a Japanese encephalitis vaccine and will need periodic boosters. Likewise with lab workers who come into close contact with the virus, as they could contract it as a result of a needlestick injury. Lab workers should make sure their vaccination records are detailed and updated.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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    • A small syringe and vaccine vial.
      By: Jonathan Vasata
      A small syringe and vaccine vial.
    • The Japanese encephalitis virus is spread by mosquitoes.
      By: hjschneider
      The Japanese encephalitis virus is spread by mosquitoes.
    • Travelers who will be in Japan for one month or longer should have a vaccination for Japanese encephalitis.
      By: HappyAlex
      Travelers who will be in Japan for one month or longer should have a vaccination for Japanese encephalitis.
    • The Japanese encephalitis vaccine offers some -- but not complete -- protection against the disease.
      By: Filip Ristevski
      The Japanese encephalitis vaccine offers some -- but not complete -- protection against the disease.