Travel Medicine

Vaccination

Japanese B Encephalitis

This mosquito-borne disease occurs in summer and autumn in the temperate regions of China, Japan, Korea, Nepal and eastern Russia. Without a typical seasonal pattern, but mainly during the monsoon season, the disease also occurs in Burma, Cambodia, southern China, India, Indonesia, Laos, Philippines, Sri Lanka, Thailand and Vietnam.

Vaccination is not recommended for the ordinary tourist, and should be based on individual risk assessment, considering the season, the travel itinerary, the type of accomodation, and the duration of exposure in travellers, the incidence of the disease is low, and the vaccine has potencial, but rare, adverse side effects. However it can be indicated for expatriates and people with prolonged stays in rural areas, pig breeding farms and rice fields, or during the monsoon season in the countries mentioned before. Vaccination during pregnancy should be avoided unless the risk of disease outweighs the theoretical risk of vaccination.

Three types of JE vaccine are commercialy available: two inactivated and one live attenuated. Inactivated mousebrain vaccine is the most used and can be given after the age of one year, by the subcutaneous route. Children with 1-2 years of age should receive half the adult dose. For the inactivated vaccines, the primary vaccination series should be given at days 0-7-28 (3 doses), or at days 0-30 (2 doses). For the live attenuated vaccine, the primary vaccination is only one dose. For all types of vaccines, one booster should be given one year later, and then every 3 years if continued protection is required. For protection, one dose of live vaccine or, at least two doses of inactivated vaccine, should be administered three weeks before departure.

These vaccines are usually available in endemic countries, and in western countries with travel medicine services.

Fernando Costa Silva, 1999 (last update: 2009)