Japanese Encephalitis Vaccine for Travelers: Exploring the Limits of Risk

Abstract

The prevention of Japanese encephalitis in travelers presents the juxtaposition of 4 factors: a disease that is widespread throughout Asia, a disease with a low incidence in travelers, a vaccine about which there are safety concerns, and a clinical course that can result in death or permanent disability in two-thirds of symptomatic cases. Travel medicine practitioners often seem to be polarized into 2 groups: a group that gives more weight to the severity of the disease (and therefore often recommend vaccination) and another group that is more persuaded by the low occurrence of cases in travelers (and therefore rarely recommend vaccination). This review assesses the known risks of contracting Japanese encephalitis and the risks associated with the vaccine and tries to develop an appropriate way to recommend this vaccine to travelers who may be at significant risk.

Recent Advances in Japanese Encephalitis

“…Although used by travellers, and in rich Asian countries, the Biken vaccine's cost and complex production have meant it has not been used widely in many countries that need it. Moreover, although the risk of serious side effects is actually comparable to other vaccines (about one in one million doses), the vaccine has developed something of a bad reputation (Shlim and Solomon, 2002). These difficulties have stimulated efforts to develop improved vaccines.…”

The Effect of Insecticide-Treated Mosquito Nets (ITMNs) on Japanese Encephalitis Virus Seroconversion in Pigs and Humans

“…32,33 A number of reports on systemic and neurological adverse effects have also raised concerns over the safety of the commercially available vaccine. [34][35][36][37][38][39] The interventional strategy using ITMNs will have an important epidemiological implication in bringing down the JEV activity in the pig-rearing communities without disturbing their social custom of rearing pigs, which they have been carrying on for ages. As well, this may provide a cost-effective way to reduce JEV transmission and supplement the relatively high cost of vaccines.…”

Prevention, diagnosis, and management of Japanese encephalitis in children

“…27 Risk is likely to be higher if the period of stay in the endemic region is longer and if involved in outdoor activities in rural areas. 28,29 Assuming an annual incidence of ten per 1,000 in the region being visited, the risk of developing the disease during a month long visit during the transmission season came to one per 5,000. 30 …”