Japanese encephalitis vaccine in travellers. Is wider use prudent?

Vaccination against Japanese encephalitis has been carried out extensively in many Asian countries for the past 20 years and is also increasingly recommended for travellers to endemic areas. Although the currently available vaccine, manufactured from mouse brain, is generally considered to be highly effective and of low reactogenicity, approximately 50% of vaccinees report experiencing usually mild adverse effects following vaccination. Concern has been raised regarding potential neurological adverse effects but the incidence of such effects appears to be very low (around 1 to 2.3 per 1000000 vaccinations). Routine vaccination of all travellers to endemic areas is clearly not beneficial at this moment and use of the vaccine should remain restricted to persons spending a month or longer in endemic areas, especially rural areas, during the transmission season. However, when counselling individual travellers, it has to be kept in mind that the possibility of Japanese encephalitis can never be ruled out completely when travelling to endemic areas, and that such an infection can prove disastrous for the individual concerned.