During the @-year study period , @ cases of hepatitis E were identified ; @ cases were confirmed in the vaccine group ( @ cases per @,@ person-years ) , and @ cases in the control group ( @ cases per @,@ person-years ) , representing a vaccine efficacy of @ % ( @ % confidence interval , @ to @ ) in the modified intention-to-treat analysis , rather than ( @ % confidence interval , @ to @ ) -LSB- corrected -RSB- .