Persistence of antibodies acquired by natural hepatitis E virus infection and effects of vaccination.

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]