[Abstract] Hepatitis E caused by hepatitis E virus (HEV) is one of the most common， enterically transmitted forms of viral hepatitis. At least 20 million cases of HEV are reported every year. HEV causes usually an acute， self-limited infection but frequently results in fatal disease in pregnant women and chronic infection in immunocompromised patients. Current treatment consisting of pegylated interferon and ribavirin is non-specific and has considerable side effects. A vaccine based primarily on inducing neutralizing antibodies has been developed but it is currently only licensed in China. The vaccine used a truncated ORF2 amino acid (aa) sequence of genotype (gt) 1 to neutralized gt 4 ......