Long-term immunogenicity and immune persistence of live attenuated and inactivated hepatitis a vaccines: a report on additional observations from a phase IV study

Abstract Objectives Our objective was to evaluate and compare long-term immunogenicity and immunological persistence of inactivated (HA-I) and live attenuated (HA-L) hepatitis A vaccines. Methods: A phase IV clinical trial (NCT02601040) was performed in 9000 participants over 18 months of age. Geometric mean concentrations (GMCs) and seroconversion rates (SRs) were compared at 5 time points during 3 years for 1800 individuals among them. Results: The SRs of HA-L and HA-I were 98.08% (95% CI: 95.59-99.38%) and 99.64% (95% CI: 98.93-100.00%) respectively 28 days after administration of the first dose, and remained at 97.07% (95% CI: 94.31-98.73%) or above and 96.73% (95%CI: 94.07-98.42%) or above respectively during the following 3 year. The GMCs for both the HA-L and HA-I groups showed that both vaccines elicited high anti-HAV titers, considerably more than the threshold of protection needed against HAV infection in humans, and these titers were sustained. Conclusions: Both HA-I and HA-L vaccines could provide an excellent long-term protective effect, and supported the routine use of both vaccines.