Japanese B encephalitis, an uncommon but serious infection, is endemic throughout most of the Far East and South East Asia. Symptoms include headache, reduced consciousness, spacticity fits, and about half the survivors are left with neurological damage.. The incubation period is between 5 to 15 days

The causal virus is transmitted by rice field breeding mosquitoes. Pigs, horses and wild birds are the amplifier hosts. The proximity of pigs to humans increases the chance of transmission. Immunisation is the only practicable way to prevent disease. Protective efficacy is 95%. Some authorities claim that the vaccine provides some protection against Dengue but evidence of this is unreliable.

Vaccination is recommended for travellers spending more than 4 weeks in rural areas of Asia, particularly i f travel is during the wet season, and/or there is considerable outdoor activity and/or the standard of accommodation is suboptimal. Vaccination is also recommended for expatriates spending a year or more in Asia (excluding Singapore) even in urban areas
(  p 47. Australian Immunisation Handbook, 8th Edition  &  Part 3.12, 'Japanese encephalitis').

New Vaccines

(a) JESPECT inactivated CSL vaccine (called 'Ixiaro' overseas) - approved product information

• registered for children 18 years old and above
• 2 injections 28 days apart (currently approx $130/dose)

(B) IMOJEV (licensed in august 2010) - a live-attenuated virus based on Yellow Fever vaccine

• registered as single dose for children 12 months old and above
• 93% seroconversion after 14 days (88% seropositive at 48 months compared to 28% with JE-VAX)
• Boosters - no clear recommendation as yet

Dosage of old vaccine JE-VAX

• 3 doses of vaccine given subcutaneously at 0, 7 or 14, and 30 days.
• 1ml for adults and children over 3 and 0.5ml for 1 - 3 years.
• Confers 99% immunity for 3 dose regeime and boosters every 3 years.
• Vaccine is quite reactogenic with serious reactions in 0.6% of vaccinees.
• Wheeze,urticaria and erythema multiforme can occur up to 10 days after vaccination.
• Persons with a past history of urticaria appear to have a greater risk of reactions.

DHS information: www.dhs.vic.gov.au/phb/
Overseas information: http://www.cdc.gov/travel/jenceph.htm
Disease outbreaks: http://www.who.int/csr/don/en/

Last edit: 23 August, 2011

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