Vaccines: Japanese Encephalitis

Specific vaccination recommendations vary among countries or even within a given country. Local or country-specific guidelines should be consulted.

1. Vaccines: The only Japanese encephalitis virus (JEV) vaccine licensed in Canada contains inactivated JEV replicated in Vero cells. Live attenuated vaccine is used in several countries in Asia.

2. Indications: Vaccination may be considered in travelers planning a stay of ≥1 month in high-risk areas or short, frequent stays in endemic regions. It should also be considered in travelers planning shorter stays in endemic regions during the seasons of JEV transmission, in those whose travel is associated with an increased risk of infection because of their itinerary. Vaccination is not recommended in individuals planning a short travel (ie, <1 month), limited to urban areas or outside of the season of JEV transmission.

The likelihood of acquiring JEV is very low, even in travelers to endemic regions. The baseline risk to Canadian travelers is estimated at 1 case of JEV infection per 11,650,000 trips to an endemic region. The number needed to vaccinate to prevent one JEV infection or death in Canadians is 12 million and 49 million patients, respectively. If this number of vaccines were to be administered, ~5 million vaccine-related adverse events would occur. As a result, the Committee to Advise on Tropical Medicine and Travel (CATMAT) recommends against routine vaccine use in those who travel to endemic areas. The CATMAT advises health-care providers to weigh individual risk tolerances, travel itinerary, and vaccination cost when determining whether a patient should receive the JEV vaccine.

3. Contraindications: General contraindications for all inactivated vaccines.

4. Immunization schedule: The primary adult vaccination series consists of 2 doses administered IM at a 28-day interval and completed ≥1 week prior to the potential exposure. An accelerated schedule, if there is insufficient time to immunize a patient prior to exposure and vaccination is indicated: 2 doses at a 7-day interval in individuals aged 18 to 65 years. A booster dose in the case of potential re-exposure: 1 dose after 12 to 24 months; or 12 months following the primary series for continued exposure. A subsequent booster dose is administered in the case of potential exposure after 10 years from the last dose. In adults aged ≥65 years, a booster dose may be considered earlier than 12 months from the date of completion of the primary series.

5. Adverse events: The JEV vaccine is generally well tolerated, with an overall adverse event rate of 14.8 per 100,000 doses.