Encephalitis Vaccine.

The Independent General Practice

Japanese Encephalitis Vaccine Information

Japanese Encephalitis is a rare but serious arboviral infection which occurs in most of the Far East and South East Asia countries. The endemic zone extends from India and Nepal across the whole of South East Asia to Japan and Korea in the Far East. It is transmitted by the bite of an infected mosquito just like malaria but it is a viral infection rather than a protozoan as in malaria.

Mosquitoes become infected by feeding on domestic pigs and wild birds infected with the Japanese encephalitis virus. Infected mosquitoes then transmit the Japanese encephalitis virus to humans and animals during the feeding process although the illness cannot be passed on from person to person. Mild infections can sometimes occur without apparent symptoms other than mild fever with headache. More severe infection is marked by quick onset, headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions (especially in infants) and spastic paralysis.

The risk of infection is greatest in long term visitors to rural areas, but the risk to short term visitors and visitors to major cities is small. There is an effective vaccine available and should be considered by anyone travelling to Asia for more than a month or visiting rural areas. However, precautions against mosquito bites will also greatly reduce the chances of infection.

It is usually mild but in some cases it can cause inflammation (swelling) of the brain (encephalitis), leading to permanent brain damage or death.

High Risk Areas:

tropical north east Australia and East Asia - including China, Myanmar (Burma), Thailand, Vietnam, Cambodia, Laos, Nepal, India, Philippines, Sri Lanka, Korea, Malaysia, Indonesia and Singapore.


The Japanese encephalitis vaccination is recommended for anyone travelling to a high-risk area who will be:


Staying for a month or longer, especially in rural areas or just after or during the monsoon season. Visiting rice fields or travelling close to pig farming areas, even if only for a short time Cycling, camping or working in fields, even if only for a short time.

The need for immunisation should be assessed on a case-by-case basis, taking into account the length of stay, activity, and the season.

Short-term travellers and those who restrict their visits to urban areas are at very low risk.

Occasionally immunisation should be considered for shorter trips where there is a higher risk of exposure.

Certain activities may increase this risk, e.g. fieldwork, camping or cycling in rural areas. If engaging in these activities, shorter trips may then pose a higher risk.

Long-term travellers and expatriates are at higher risk, those staying a month or longer in endemic areas, visiting or working in rural agricultural areas such as pig farms, rice fields and marshland should consider immunisation.

All travellers should be advised to take mosquito bite precautions especially during the cooler hours at dawn and dusk when the mosquito feeds.

Vaccine Information


The course needs to be completed at least 10-14 days before you leave in case of an allergic reaction. The vaccine£requires two doses, with the second dose given 28 days after the first. The vaccine will require a booster between 12 months and 24 months later. This will provide a further 12 months cover This vaccine is only£licensed for people£aged over 18 and not recommended for children. There is no data on the duration of protection a course provides.

Vaccine side effects:

After having the Japanese encephalitis vaccine, around 20% of people develop temporary soreness, redness and swelling at the injection site. About 10% of people who have the vaccine experience other side effects such as:

a high temperature (fever) of 38C (100.4F) headache tiredness chills dizziness nausea or vomiting abdominal pain


Any allergic reaction usually occurs within minutes of having the injection, although in some cases it can be delayed for up to 2 weeks. This is why the course should be completed at least 10-14 days before you travel. Details of possible side effects and special precautions should be discussed during the appointment.

Please be aware that for full immunity some vaccination courses, with more than one vaccine required, may take up to a month or longer. Please, also be aware that many vaccinations will not become fully effective until weeks after the course completion. It is strongly advised that you leave plenty of time to complete the course before your trip. Intervals between different vaccines or doses are recommended, which allows time for antibodies to be produced and any reaction to the vaccine to subside.

The above information should only be used as a guide and is not a substitute for medical advice. All vaccinations are only carried out following a Travel Risk Assessment and Consultation. The brand of vaccine we supply may also vary depending on the current supply status of a particular vaccine.

In order for us to assess the most appropriate vaccines please complete our Travel Risk Assessment.


Travel Risk Assessment
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