Comparison of Immunization Schedules of Inactivated Hepatitis A Vaccine and Combined Hepatitis A and Hepatitis B Vaccine

Inclusion Criteria: * Healthy infants between 18 and 24 months old; * Have not received hepatitis A vaccine before; * Completed hepatitis B vaccine full immunization schedule; * Written consent of the guardian of each participant; Exclusion Criteria of the First Injection: * History of allergy to vaccine(s), or history of serious adverse reaction to vaccination, such as urticaria, dyspnea, angioneurotic edema, or abdominal pain; * Autoimmune disease or immunodeficiency; * Any acute disease that made the conditions of the person unsuitable for vaccination * Administration of any live attenuated vaccine within 14 days prior to the injection; * Administration of any subunit vaccine or inactivated vaccine within 7 days prior to the injection; * Administration of treatment of immunosuppressants (e.g., corticosteroid) within 1 month prior to the injection, or planning for such treatment during this study; * Body temperature \> 37.0 °C before injection; * Based on the evaluation of the investigator, there was any other factor that indicating the person was unsuitable for this study; Exclusion Criteria of the Second Injection: * Any acute infectious disease, body temperature \> 38.5 °C or acute attacks of chronic diseases within 3 days prior to the second injection; * Administration of blood product or other investigational drug during this study; * Occurrence of adverse event at grade 3 or higher and the event was related to the first injection; * The investigator or the Ethic Committee decided that the subject should be excluded;