Hepatitis E virus is a common cause of illness worldwide and is associated with severe complications, especially in pregnant women. In this report, the long-term efficacy, immunogenicity, and safety of a hepatitis E vaccine are described. Hepatitis E virus (HEV) is a common cause of acute hepatitis worldwide. 1 , 2 HEV infection occurs in two distinct epidemiologic patterns. 3 The most common pattern is waterborne infection, which is caused by HEV genotype 1 or 2 and occurs mainly in resource-limited countries, often in large, protracted outbreaks or in sporadic cases associated with high mortality among pregnant women. 4 – 6 The other pattern is transmission from animals and humans, which is caused by HEV genotype 3 or 4 and occurs widely in both resource-limited and developed countries. 1 , 7 – 9 Rein et al. 10 estimated the incidence of hepatitis E in areas . . .