Abstract
Hepatitis E virus (HEV) infection is a major cause of acute viral hepatitis worldwide. The efficacy and safety of the HEV239 vaccine have been validated, with protection lasting at least 10 years. This study extended the phase 3 trial of HEV239 (NCT01014845), presenting data on the durability of the anti-HEV IgG response elicited by one or two doses in the participants with different baseline serostatus. Over half of baseline seronegative individuals retained detectable antibodies at month 91 after two doses, with geometric mean concentration levels above the detection limit at month 67 (no available data for month 91). Seropositive individuals exhibited more prolonged and higher anti-HEV IgG response. After a single dose, individuals with pre-existing immunity achieved high and sustained antibody levels for over 103 months, comparable to the two-dose regimen. Both single-dose and two-dose HEV239 regimens demonstrated notable immunogenicity and persistence, potentially offering substantial protective benefits.