In the previous double-blind, randomized, phase IV clinical trial in 2008, 300 healthy Chinese children aged 18 to 35 months old were administered with one dose of inactivated and attenuated alive hepatitis A vaccine. Series of serum samples were taken for immunogenicity and immune persistence evaluation. Safety observations were performed after vaccination. This trial was also approved by Tianjin CDC Biomedical Ethics Committee in 2008.