A double-blind, randomized and controlled clinical trial was conducted in healthy children aged from 1 to 8 years to evaluate the immunogenicity and safety of three consecutive lots of a preservative-free inactivated hepatitis A vaccine (Healive®).

Participants who completed their primary vaccination were invited to participate in the follow-up phase. Written informed consents were obtained from them. The follow-up study was open-label. These subjects were visited in the next 11 years for blood sampling and assessment of immune persistence induced by vaccination.

The investigated vaccine is an inactivated, adjuvanted and preservative-free hepatitis A vaccine. Each dose contained 250 U HAV antigen in 0.5 milliliter.

Total 400 subjects were enrolled and assigned into four groups, each receiving one of the three lots of Healive® or an established control vaccine at month 0 and 6. Anti-HAV titers were determined at month 1, 6 and 7. Anti-HAV titer over 20 mIU/ml is defined as seroprotection.

After the full immunization schedule, written informed consents were obtained from subjects who would like to participate in the follow-up study. Blood samples of these subjects were collected at month 18, 30, 42, 54, 66, 112,138 after the first injection to evaluate the seroconversion rates (SCRs) and geometric mean concentrations (GMCs) of antibody against hepatitis A virus. Serological results of the follow-up study were then used to explore suitable statistical model for predicting the persistence of hepatitis A vaccine-induced antibodies.

Inclusion Criteria:

• Health children from 1 to 10 years
• Not participate in any other trial during the course of the trial
• Informed consent

Exclusion Criteria:

• Any history of allergic reactions or convulsions following vaccination
• Other known or planned vaccination within 1 month prior to the study and during the study period
• Any chronic illness/disease including virus hepatitis, tuberculosis and epilepsy
• Presence of any congenital abnormality, upgrowth obstacle
• Any history/suspicion/presence of neurology and Lunacy
• Any current or foreseeable use of immunosuppressors (i.e. corticosteroids , immunoglobulins) within 1 month prior to the vaccination and during the period of the study
• Contraindication to intramuscularly injection due to thrombocytopenia or other bleeding disorders
• Abnormal ALT
• Positive markers for anti-HAV and HBV（HBsAg）infection
• Presence of fever at the time of vaccination, i.e. body temperature (by mouth) > 37.0 centigrade.