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Immunity acquired from infection or vaccination protects humans from symptomatic hepatitis E. However, whether the risk of hepatitis E virus (HEV) infection is reduced by the immunity remains unknown. To understand this issue, a cohort with 12 409 participants randomized to receive the hepatitis E vaccine Hecolin(®) or placebo were serologically followed up for 2 years after vaccination. About half (47%) of participants were initially seropositive. A total of 139 infection episodes, evidenced by four-fold or greater rise of anti-HEV level or positive seroconversion, occurred in participants who received three doses of treatment. Risk of infection was highest among the baseline seronegative placebo group participants (2.04%). Pre-existing immunity and vaccine-induced immunity lower the risk significantly, to 0.52% and 0.30%, respectively. In conclusion, both vaccine-induced and naturally acquired immunity can effectively protect against HEV infection., (© 2013 The Authors Clinical Microbiology and Infection © 2013 European Society of Clinical Microbiology and Infectious Diseases.)

Objective Naturally acquired anti–hepatitis E virus (HEV) immunity can protect against new HEV infections. The aim of this study was to analyse the persistence of naturally acquired anti-HEV immunoglobulin (Ig) G and anti-HEV IgG concentrations after vaccination. Methods We examined the seropositivity rates of participants included in a phase 3 clinical efficacy trial (67 months' follow-up) for a HEV vaccine (Hecolin; Xiamen Innovax Biotech, China) and predicted long-term persistence using mixed-effect models. Results The analysis focused on 2242 baseline seropositive participants in a control group (placebo recipients) and 2031 baseline seropositive participants in an vaccine group (vaccine recipients) who received 1 to 3 doses of Hecolin. Naturally acquired anti-HEV IgG levels decreased steadily independent of the initial antibody level; 50% of the placebo recipients were expected to have undetectable antibody concentrations after 14.5 years. After immunization with Hecolin, the power-law model and the modified power-law model predicted that 82.1 and 99.4% of the participants, respectively, would remain seropositive for anti-HEV IgG for 30 years after vaccination. Conclusions Whereas naturally acquired anti-HEV IgG levels decrease steadily, HEV vaccination induces long-lasting, high-level anti-HEV IgG concentrations. [ABSTRACT FROM AUTHOR]