Japanese encephalitis: update on vaccines and vaccine recommendations

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.

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.

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.