Japanese encephalitis: update on vaccines and vaccine recommendations

PURPOSE OF REVIEW: Japanese encephalitis is the most common vaccine-preventable viral encephalitis in Asia. In view of the production cessation of the inactivated mouse brain-derived Japanese encephalitis vaccine, it is timely to provide an update on new Japanese encephalitis vaccines and revised vaccine recommendations. RECENT FINDINGS: A new inactivated, adjuvanted, Vero cell-culture-based Japanese encephalitis vaccine, IC51, was licensed in Europe and the United States in 2009. Administered in a two-dose regimen at 0 and 28 days, it was shown to be well tolerated and produce high seroconversion rates. In addition, Chimerivax Japanese encephalitis, a novel live-attenuated one-dose chimeric vaccine comprising the structural genes of SA 14-14-2 virus and nonstructural genes of yellow fever 17D virus, is in the process of getting licensed in Australia and in south east Asia. SUMMARY: Previous recommendations for Japanese encephalitis vaccination of travelers were predicated on minimizing exposure to a mouse-brain-derived vaccine with a poorly understood and worrisome safety profile, whereas the risk of acquiring Japanese encephalitis itself during travel was assessed to be relatively low. With the availability of a new cell-culture-derived vaccine IC51 with an excellent safety profile, it is appropriate to reconsider benefit-risk considerations for the vaccination of travelers. These considerations are reflected in the March 2010 revised recommendations by the United States Advisory Committee on Immunization Practices.