Do I Need to Get the Japanese Encephalitis Vaccination?

This is a common question for travellers to South and Southeast Asia. The answer is probably not, but it depends. The level of risk for acquiring Japanese Encephalitis (JE) varies a lot depending on your trip — where you are going, how long you will stay and what you will be doing.

What is Japanese encephalitis and where does it occur?

Japanese Encephalitis is a viral disease that is transmitted through the bite of an infected mosquito. In humans, JE causes inflammation of the membranes around the brain. Most infections of JE are mild with just a fever and headache or without any symptoms at all. But about 1 in 200 infections lead to serious disease, characterized by a sudden high fever, headache, neck stiffness, disorientation, coma, seizures and death. Among those cases where disease symptoms are present, 30% of those who survive also suffer from lasting damage to the central nervous system.

JE occurs throughout most of Asia and some areas of the western Pacific. The expansion of irrigated rice production systems in South and Southeast Asia has had a big impact on the disease burden because the flooded rice fields offer a perfect breeding ground for the mosquito that transmits JE.

Who is at risk for Japanese encephalitis?

The risk for most travellers is very low — the overall incidence of JE among people from countries where JE does not occur travelling to Asia is estimated to be less than 1 case per 1 million travellers.

However, the level of risk varies greatly depending on your destination, the duration of your stay, the season and the activities you partake in during your travels.

Destination

Obviously, you are at greater risk for JE if you are visiting a country where JE is endemic. But, it also depends on where you travel within that country. If you are staying in major urban centres, the risk is minimal. Rural and agricultural regions with rice production and pig rearing are the highest risk areas because the rice fields provide a breeding ground and pigs are amplifying hosts for the virus (the virus reproduces in the pig and then mosquitoes that bite the pig will probably become infected).

Duration

The longer you stay in a country with JE, the higher your risk for infection. The risk of getting JE among expatriates and travellers who stay for prolonged periods in rural areas is similar to the risk among the resident population.

Season

May to October are the months in which most transmission occurs for the majority of countries with JE risk. You can find a nice table from the CDC that summarizes the risk for Japanese encephalitis by country and season here or you can quickly view a specific country using Sitata.

Activities

Travellers who participate in outdoor activities, especially during the evening or night are also at higher risk as the mosquito that transmits JE prefers to bite after sunset and during the night.

The Bottom Line

The JE vaccine can help to reduce the risk of acquiring the disease, but it is expensive (around $200 per shot). There is no way to completely eliminate the risk of JE, but when the likelihood of getting JE is significant, the JE vaccine can help minimize this risk.

Our general recommendations for the JE vaccine are:

• Long-term travellers (1 month or longer) to endemic areas during the JE transmission season.
• Short term travellers (less than 1 month) to endemic areas who plan to visit rural areas and engage in activities that will put them at higher risk for mosquito bites (outdoor activities, no bed nets, etc.)
• Travellers to areas with an ongoing JE outbreak. Check our country specific travel alerts to stay up to date.
• Travellers to endemic areas who are uncertain of their travel plans, as they may end up in a rural, high-risk area.

It’s important to remember that all travellers should do everything they can to avoid mosquito bites to reduce the risk of acquiring JE, along with other diseases like malaria. Using insect repellent, sleeping under permethrin-impregnated bed nets, and staying in accommodations with screens will all help to reduce the risk of insect bites.

For most travellers, the JE vaccine is not necessary but it’s not always an obvious decision. If you are still unsure about whether you need the JE vaccine after reviewing your travel plans, you can always consult with Sitata or your local travel medicine clinic.