Japanese encephalitis primary prevention
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The control of Japanese encephalitis is based essentially on three interventions: mosquito control, avoiding human exposure to mosquitoes and immunization. Mosquito control has been very difficult to achieve in rural settings and avoidance of exposure is difficult as Culex mosquitoes bite during day time. Immunization is the only effective method for sustainable control. Routine immunization of school-age children is currently in use in Korea, Japan, China, Thailand and Taiwan. The introduction of the JE vaccine into the Expanded Program of Immunization has helped curb the disease in countries like Thailand, Vietnam, Sri Lanka and China[1].
Primary Prevention
- Use insect repellent and wear long pants and sleeves
- Sleep in air-conditioned or well-screened rooms or use bednets
- A vaccine against JE virus is available.
Vaccine
Infection with Japanese encephalitis virus confers life-long immunity. All current vaccines are based on the genotype III virus. A formalin-inactivated mouse-brain derived vaccine was first produced in Japan in the 1930s and was validated for use in Taiwan in the 1960s and in Thailand in the 1980s. The widespread use of vaccine and urbanisation has led to control of the disease in Japan, Korea, Taiwan and Singapore. The high cost of the vaccine, which is grown in live mice, means that poorer countries have not been able to afford to give it as part of a routine immunization programme.
In the UK, the two vaccines used (but which are unlicensed) are JE-Vax® and Green Cross. Three doses are given at 0, 7–14 and 28–30 days. The dose is 1ml for children and adult, and 0.5ml for infants under 36 months of age.
The most common adverse effects are redness and pain at the injection site. Uncommonly, an urticarial reaction can develop about four days after injection. Because the vaccine is produced from mouse brain, there is a risk of autoimmune neurological complications of around 1 per million vaccinations.
Neutralising antibody persists in the circulation for at least two to three years, and perhaps longer.[2][3] The total duration of protection is unknown, but because there is no firm evidence for protection beyond three years, boosters are recommended every two years for people who remain at risk.
- U.S. Expatriates: Japanese encephalitis vaccine is recommended for persons who plan to reside in areas where Japanese encephalitis is endemic or epidemic (residence during a transmission season). Risk for acquiring Japanese encephalitis is highly variable within the endemic regions. The incidence of Japanese encephalitis in the location of intended residence, the conditions of housing, nature of activities, and the possibility of unexpected travel to high-risk areas are factors that should be considered in the decision to seek vaccination.
- Travelers: JE vaccine is recommended for travelers who plan to spend at least 1 month in endemic areas during the JE virus transmission season. Vaccine should also be considered for the following:
- Short-term (less than 1 month) travelers to endemic areas during the transmission season, if they plan to travel outside an urban area and their activities will increase the risk of exposure. Higher-risk activities include participating in extensive outdoor activities (such as camping, hiking, trekking, biking, fishing, hunting, or farming) and staying in accommodations without air conditioning, screens, or bed nets.
- Travelers to an area with an ongoing outbreak.
- Travelers to endemic areas who are uncertain of specific travel destinations, activities, or duration.
References
- ↑ Tauber E, Dewasthaly S (2008). "Japanese encephalitis vaccines--needs, flaws and achievements". Biol Chem. 389 (5): 547–50. PMID 18953721.
- ↑ Gambel JM, DeFraites R, Hoke C; et al. (1995). "Japanese encephalitis vaccine: persistence of antibody up to 3 years after a three-dose primary series (letter)". J Infect Dis. 171: 1074.
- ↑ Kurane I, Takashi T (2000). "Immunogenicity and protective efficacy of the current inactivated Japanese encephalitis vaccine against different Japanese encephalitis virus strains". Vaccine. 18 Suppl: 33&ndash, 5.