Japanese encephalitis vaccine in travelers.

Extensive vaccination against Japanese encephalitis (JE) has been carried out in many Asian countries for the past 20 years and is also increasingly recommended for travelers to endemic areas. Concerns have been raised regarding potential neurological and allergic side effects of the currently available JE vaccine, which is manufactured from mouse brain. A new purified, inactivated JE virus vaccine (IC51) has been developed, which is manufactured in a Vero cell culture substrate. Studies show that the vaccine is both safe and immunogenic and the product will be licensed very soon for use in many industrialized countries. Once a highly immunogenic and safe product is available, wider use of JE vaccine in travelers will be prudent. Currently, vaccination is restricted to travelers with an increased risk of acquiring JE. Individuals at increased risk have been defined quite arbitrarily as travelers with increased behavioral contact to JE-transmitting mosquitoes, in particular, during stays in rural areas and during the transmission season. However, the possibility of an infection with JE virus can never be ruled out when traveling to endemic areas and infection can prove disastrous for the individual concerned. Since a safe product will be available very soon, guidelines and recommendations will have to be reconsidered.