Here is the World Health Organization (WHO) statement regarding the use of JE vaccine in travelers
“The risk for Japanese encephalitis for most travellers to Asia is very low but varies
according to season, destination, duration of travel and activities. The risk is
higher in long-term travellers and expatriates. The risk to short-term travellers and
those who travel mainly to urban areas is very low.
Vaccination is recommended for travellers with extensive outdoor exposure (camping, hiking, bicycle tours, outdoor occupational activities, in particular in areas where flooding irrigation is practised) in rural areas of an endemic region during the transmission season.”
(From WHO Green Book, International Travel and Health 2010)
Here is the US CDC recommendation about the use of JE vaccine in travelers. They divide into 2 categories;
1 JE vaccine is recommended for travelers who plan to spend a month or longer in endemic areas during the JEV transmission season. This includes long-term travelers, recurrent travelers, or expatriates who will be based in urban areas but are likely to visit endemic rural or agricultural areas during a high-risk period of JEV transmission.
2 JE vaccine should be considered for the following persons:
2.1 Short-term (<1 month) travelers to endemic areas during the JEV transmission season if they plan to travel outside of an urban area and have an increased risk for JEV exposure. Examples of higher-risk activities or itineraries include 1) spending substantial time outdoors in rural or agricultural areas, especially during the evening or night; 2) participating in extensive outdoor activities (e.g., camping, hiking, trekking, biking, fishing, hunting, or farming); and 3) staying in accommodations without air conditioning, screens, or bed nets.
2.2 Travelers to an area with an ongoing JE outbreak.
2.3 Travelers to endemic areas who are uncertain of specific destinations, activities, or duration of travel.
JE vaccine is not recommended for short-term travelers whose visit will be restricted to urban areas or times outside of a well-defined JEV transmission season.
(From the US CDC Yellow Book. International Health 2010)
In the past, most experts are very careful when going to recommend JE vaccine in travelers since only mouse-brain derived vaccine is available. But now we have new safer vaccine, most experts fell easier when recommend JE vaccine.
What’s about our opinion regarding the use of JE vaccine? Firstly, we will assess the risk individually and will inform the travelers about the disease and their risk and will discuss with travelers.
Basically, we will recommend JE vaccine for travelers in Southeast Asia who will stay here more than 2-3 wks, especially who will travel in rural area and may expose with mosquito. We do not pay special concern to seasonality, since transmission of JE in Southeast Asia could occur all year round.
By the way, apart from the vaccine, we will emphasize on the importance of mosquito bite prevention also.