Japanese encephalitis

Preventing Japanese encephalitis

You can reduce your risk of Japanese encephalitis by getting vaccinated and by taking precautions to avoid mosquito bites when in at-risk areas.

Japanese encephalitis vaccination

Vaccination against Japanese encephalitis is recommended for anyone who may be at risk of the infection through their work or travels. It provides protection for more than 9 out of every 10 people who have it.

Vaccination is particularly important if you are visiting a high-risk area during the rainy season and you are going to visit rural areas (such as rice fields or marshlands), or take part in any activities that may increase your risk of becoming infected (such as cycling or camping).

If you are travelling to a country where Japanese encephalitis is found, visit your GP or practice nurse at least six to eight weeks before you leave, to discuss whether you should have the vaccination. For more information about at-risk areas, read about the causes of Japanese encephalitis.

The vaccine

There is one vaccine for Japanese encephalitis currently licensed in the UK for use in adults and children over two months old. 

The vaccination is given as an injection and requires two doses for full protection, with the second dose given 28 days after the first. The second dose should ideally be completed at least a week before travelling.

The Japanese encephalitis vaccine is not usually available on the NHS, and each dose will normally cost about £70-75 per person. It's a good idea to include this when budgeting for your trip.

If you continue to be at risk of infection, a booster dose of the vaccine should be given between 12 and 24 months after you are first vaccinated.

Side effects

Up to 40% of people who have the Japanese encephalitis vaccine experience mild and short-lived side effects, such as soreness, redness or swelling at the site of the injection, a headache and muscle pain. More serious side effects – such as a raised, itchy red rash (urticaria or hives), swelling of the face and difficulty breathing – are rare.

If you develop any worrying symptoms after being vaccinated, contact your GP as soon as possible or call NHS 111 for advice.


Most people can have the Japanese encephalitis vaccination safely, but you should tell the doctor or nurse before being vaccinated if you have a high temperature (fever), or if you are pregnant or breastfeeding.

The vaccination may need to be postponed if you have a fever. It may also not be recommended if you are pregnant or breastfeeding, due to the theoretical risk of problems resulting from the vaccine being passed to your baby.

The Japanese encephalitis vaccine is not normally recommended for children less than two months old because it is unclear how safe and effective it is for this age group. 

You should not have the vaccine if you have had a severe allergic reaction (anaphylaxis) to it or any of its ingredients in the past.

Avoiding mosquito bites

As the vaccination against Japanese encephalitis is not 100% effective, you should protect yourself against mosquito bites while travelling or staying in at-risk areas by:

  • sleeping in rooms with close-fitting gauze over the windows and doors
  • if this is not possible or you are sleeping outside, use mosquito nets that have been impregnated with an insecticide, such as permethrin
  • spraying your room with insecticide in the early evening to kill any mosquitoes that have got in during the day
  • cover up with long-sleeved tops, trousers and socks – mosquitoes that carry the Japanese encephalitis virus are usually most active at dusk and enjoy warm, humid conditions
  • wearing loose-fitting clothes, as mosquitoes can bite through skin-tight clothing 
  • applying a good-quality insect repellent to any exposed areas of skin (see below)

Insect repellent

Various types of insect repellent are available. Many contain diethyltoluamide (DEET), but some are available that contain dimethyl phthalate, or eucalyptus oil if you are allergic to DEET.

When using insect repellent, make sure you:

  • don't use it on cuts, wounds or irritated skin
  • don't get it in your eyes, mouth and ears
  • don't spray it directly onto your face  spray it onto your hands and then apply it to your face
  • don't allow young children to apply it themselves  put it on your hands and then apply it to your child
  • apply it after applying sunscreen, not before
  • wash your hands thoroughly after use and wash the repellent off your skin with soap and water when it is no longer needed
  • always follow the manufacturer's instructions

If you or your children have a reaction to an insect repellent, such as redness, stop using it. Wash it off and contact your GP, or a local healthcare professional if you are abroad.

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