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Promoting prevention
Although the disease is uncommon in travellers
, the consequences can be very serious
. Providing quality pre-travel health advice for a disease that is rare but potentially deadly , and where vaccination incurs inconvenience and expense , is a challenge . Historically , the rate of JE vaccination uptake in Australian travellers has been low . In a records audit conducted in a specialised travel clinic , the rate of vaccination in people travelling to JE risk areas was found to be 28 %. 5 This is likely to be considerably lower in a general practice setting . Prevention of JE involves avoiding mosquito bites , especially for travellers staying overnight in rural areas of risk . This includes use of personal repellent , covering up with clothing , screened accommodation or bed nets , insecticide sprays and other measures to kill or repel mosquitoes and minimise breeding sites .
A risk assessment is needed to determine which travellers should be vaccinated . The Australian Immunisation Handbook recommendations provide a foundation , but applying these to the individual traveller can be challenging . Although it does not have a specific recommendation for travellers to Papua New Guinea who are walking the Kokoda Track , given the extent of outdoor activity , vaccination should certainly be considered in this group . To assist with
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risk assessment , Professor Colleen Lau and colleagues from the University of Queensland have developed an interactive online JE vaccination risk-benefit analysis tool . The tool is still in Beta ( trial ) version but is available for use ( see online resource ). The tool provides an estimate of risks if vaccinated compared to unvaccinated and also an estimate of risk of adverse effects of the vaccine . The tool developers welcome user feedback .
Practical considerations with vaccination
There are two JE vaccines currently available
in Australia . One option is JEspect , a Vero cell derived JE vaccine containing inactivated 14-14-2 strain virus . JEspect can
Some patients travelling to areas of risk may present too late to complete the course .
be used from the age of two months and is given by IM injection in a two-dose regimen on day zero and day 28 . It takes until day 35 ( ie , one week after the second dose ) for a high level of seroprotection to be achieved . This dose interval raises practical problems as some patients travelling to areas of risk may present too late to complete the course prior to departure . A booster dose is needed at 12-24 months if there is ongoing
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transmission risk . The cost for the two-dose course is approximately $ 150- $ 200 . The vaccine ( under the brand name Ixiaro ) is available in some , but unfortunately not all , countries with JE risk .
The other option is Imojev , a live attenuated vaccine . Imojev can be given from the age of nine months . Only one subcutaneous dose is required and a seroprotective level of antibodies is generally reached 14 days after vaccination . Booster doses are not needed in those aged 18 years and older but in those aged under 18 a booster dose is needed 12-24 months after initial dose if at ongoing risk . The cost of Imojev is approximately $ 250- $ 300 .
Given the high cost and pressures on supply of JE vaccines , Australian researchers including Dr Deborah Mills and Professor Lau have been investigating the immunogenicity of a fractional dose ( 0.1ml ) of Imojev . Their findings , published in the Journal of Travel Medicine , showed good short-term immunogenicity . 6 Longer-term studies are needed , and though not yet recommended in travellers , ATAGI has stated that intradermal administration of Imojev live JE vaccine may be used as a dose sparing strategy in settings where public health benefit outweighs potential risks .
References on request from kate . kelso @ adg . com . au
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Online resource
Prevention involves avoiding mosquito bites , especially for travellers staying overnight in rural areas of risk .
• Japanese encephalitis vaccination risk / benefit analysis tool vaxical . com
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