Japanese encephalitis

Japanese encephalitis (JE) is a viral infection of the brain transmitted to humans by mosquitoes in parts of Asia and the Pacific rim. The mosquitoes that transmit JE feed predominantly during the night, from dusk to dawn and are prolific in rural areas, where rice cultivation and pig farming are common. However, they have also been found in urban locations.

The risk for most travellers to Asia is very low, especially for short-term travellers visiting urban areas. The overall incidence of JE among persons from non-affected countries travelling to Asia is estimated to be less than one case per 1 million travellers. Risk varies on the basis of: destination, duration, season and activities. It increases for persons who intend to live or travel in risk areas for long periods of time and have rural trips during transmission seasons. Certain activities, even during short trips, where there is significant rural, outdoor or night time exposure e.g. fieldwork or camping can increase the traveller’s risk.

Most human infections with Japanese encephalitis virus do not result in symptoms. When symptoms do occur they include fever, headache and confusion. In symptomatic cases requiring hospitalisation mortality rates are high and neurological complications are common.

Prevention

The risk of acquiring JE can be reduced by insect bite avoidance, particularly between the hours of dusk and dawn, when Culex mosquitoes are most active.

Japanese encephalitis vaccine

A licensed JE vaccine; IXIARO® is available and should be offered to those intending to stay for long periods in rural regions where JE occurs during the main transmission season or whose planned activities increase their risk.

Vaccination schedule

Age range

Dose

Schedule

Reinforcing immunisation

Under 2 months of age

Not usually recommended

(no safety or efficacy data)

Children aged 2 months to under 3 years

0.25ml

(discard half of the vaccine)*

2 doses:

Day 0 and 28

No data**

Children aged 3 to 11 years

0.5ml

2 doses:

Day 0 and 28

No data**

Children aged 12 to 17 years

0.5ml

2 doses:

Day 0 and 28

See also accelerated schedule***

No data**

Adults aged 18 to 65 years

0.5ml

2 doses:

Day 0 and 28

See also accelerated schedule***

Single dose of IXIARO® at 12-24 months following primary course. For those at continuous risk a booster at 12 months is recommended.

Manufacturer recommends a second booster 10 years after the first booster dose, prior to potential exposure to JEV.

Adults aged 65 years and older

0.5ml

2 doses:

Day 0 and 28

See also accelerated schedule***

Duration of protection is uncertain, therefore a booster dose (third dose) should be considered before any further exposure to JE virus. Long-term seroprotection following a booster-dose is not known.

*See IXIARO® Summary of Product Characteristics for details on preparing the 0.25 ml dose for children aged 2 months to less than 3 years. 
**There are no data to permit recommendations for boosting in infants and children below 18 years of age. However, if sustained protection is required, a booster dose may need to be considered.
***See also accelerated schedule below.

 

Accelerated schedule

Adults aged 18-65 years can be vaccinated in an accelerated schedule according to the IXIARO marketing authority as follows: first dose at day 0, second dose: 7 days after first dose. With both schedules, the primary immunisation schedule (first and second dose) should be completed at least one week prior to potential exposure to JE. Use of this accelerated schedule can also be considered off license for travellers 12-18 years of age and those over 65 years of age when time is genuinely short.

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