Japanese encephalitis

Transmission

Japanese encephalitis is is caused by a flavivirus, present in wading birds and pigs, and transferred to the Culex mosquito. It is transmitted by bites from infected Culex mosquito, which are most active from dusk to dawn.

Japanese encephalitis vaccine is recommended for travellers to rural parts of Asia and endemic parts of Australia for stays of one month or more during the main transmission season, however, it may be required for shorter stays if visiting an area of high risk such as rice fields or close to pig farms. Travel should be avoided within 10–14 days of primary course, in case a delayed allergic reaction occurs.

Vaccination schedule

Brand Vaccine information Primary course Booster
IXIARO
  • Inactivated, adsorbed
  • Licensed from 2 months of age
  • Single dose at day zero and 28
  • Accelerated schedule for adults aged 18-65 years at day 0 and day 7
  • Effective one week after second dose in adults
  • Recommended not to interchange between different  vaccines (for example, the unlicensed Green Cross vaccine)

Check the Summary of Product Characteristics (SPC) for different age group’s schedules

 

From 18 years of age

  • Third dose between 12–24 months for re-exposure
  • Continuous/repeated exposure — at 12 months

 

The information below is based on Public Health England recommendations; the SPC should be referred to for manufacturer recommendations.

Acute illness

If a patient is suffering from an acute illness, immunisation should be postponed until they have recovered. Patients with minor infections without fever or systemic upset do not need to postpone their vaccination schedule.

Administration with other vaccines

Japanese encephalitis vaccine can be given at the same time as other routine or travel vaccines as long as they are administered at different sites.

Immunocompromised patients

Japanese encephalitis vaccine can be given to patients who are immunocompromised if they are travelling to an area of risk, however, it may not be as effective. Specialist advice may be required.

Pregnancy and breast-feeding

No harmful effects due to Japanese encephalitis vaccination during pregnancy or breast-feeding have been reported so it should be considered when clinically indicated. Japanese encephalitis infection has been associated with miscarriage during the first two trimesters of pregnancy. A risk assessment should be carried out to weigh up the theoretical risks of vaccination against the risk of acquiring the disease.

Children

Green Cross vaccine is no longer recommended for use in children under the age of 17 years because Ixiaro is now licensed for use in those aged two months and older.