Japanese Encephalitis Vaccine

There are now four main types of JE vaccines currently in use: inactivated mouse brain-based vaccines, inactivated cell-based vaccines, live attenuated vaccines, and live chimeric vaccines. Traditionally, the most widely used vaccine was a purified inactivated product made from either Nakayama or Beijing strains propagated in mouse brain tissue. It is still produced and used in several countries.

Over the past years, the live attenuated SA14-14-2 vaccine manufactured in China has become the most widely used vaccine in endemic countries, and it was prequalified by WHO in October 2013. Cell-culture based inactivated vaccines have also been licensed (and one product WHO prequalified), as has a live, recombinant product based on the yellow fever vaccine strain. There are several commercial vaccines against Japanese encephalitis (JE) virus.  One known as JE-MB is produced in Japan and distributed widely and is the only vaccine available for people between one and 17 years of age.  A second vaccine known as JE-VC is produced in the United Kingdom and is recommended only for people 17 years of age or older.  Other vaccines are produced and/or marketed in China, India, Australia, New Zealand, and elsewhere.

Two inactivated cell culture-derived TBE vaccines are available in Europe, in adult and pediatric formulations: FSME-IMMUN (Baxter, Austria) and Encepur (Novartis, Germany). The adult formulation of FSME-IMMUN is also licensed in Canada. Two other inactivated TBE vaccines are available in Russia: TBE-Moscow (Chumakov Institute, Russia) and EnceVir (Microgen, Russia). Immunogenicity studies suggest that the European and Russian vaccines should provide cross-protection against all 3 TBE virus subtypes.

For both FSME-IMMUN and EnceVir, the primary vaccination series consists of 3 doses. The specific recommended intervals between doses vary by country and vaccine. Although no formal efficacy trials of these vaccines have been conducted, indirect evidence suggests that their efficacy is >95%. Vaccine failures have been reported, particularly in people aged ≥50 years.

Because the routine primary vaccination series requires ≥6 months for completion, most travelers to TBE-endemic areas will find avoiding tick bites to be more practical than vaccination. However, an accelerated vaccination schedule has been evaluated for both European vaccines, and results in seroconversion rates are similar to those observed with the standard vaccination schedule. Travelers anticipating high-risk exposures, such as working or camping in forested areas or farmland, adventure travel, or living in TBE-endemic countries for an extended period of time, may wish to be vaccinated in Canada or Europe.

Whether or not to receive this vaccine depends considerably on the itinerary of the traveller and the length of time that a traveller might visit areas where Japanese encephalitis occurs.  This disease does not usually occur in urban areas or large cities and thus may not be required for travellers to large cities.  Outbreaks, however, may occur in rural farming areas. In some countries, the Japanese enchephalitis virus may be widespread while in other countries, it may be seasonal.  Travellers should monitor Sitata alerts for outbreaks of this disease and consult their physician to determine if this vaccine is needed.

What are the side effects?

Japanese encephalitis vaccine is usually well tolerated.  Common side effects include headache, muscle aches, and pain, tenderness, redness or swelling where the injection was given.  Anyone who has ever had a serious allergic reaction to a previous dose of this vaccine should not get another dose. 

What is the dosage schedule?

Dosage schedules vary somewhat among the vaccines.  For JE-VC, a two-dose schedule with 28 days between doses is recommended.  A booster dose should be given one year after the second dose when there is potential for re-exposure to JE virus.

For the JE-MB, the dosage schedule will vary by country and by vaccine.