Hepatitis A vaccine study to see how well different doses work in adults and kids

Inclusion Criteria:

1. Healthy participants aged 1 year and older;
2. Participants (and/or their legal guardians) are able to understand and sign the informed consent voluntarily;
3. Participants of reproductive potential and their sexual partners should voluntarily use effective contraception from signing the ICF to 30 days after the second vaccination and avoid donating sperm or eggs.
4. Participants should provide verifiable identification, to be contacted, and to contact the investigator during the study period.
5. Participants should agree to comply with the lifestyle precautions outlined in the protocol.

Exclusion Criteria:

1. Prior vaccination with any hepatitis A vaccine or combined vaccines containing HAV components;
2. Prior history of HAV infection;
3. Female participants of reproductive potential who are pregnant (including a positive urine pregnancy test) or have a pregnancy plan within 30 days after the second vaccination, or who are currently lactating;
4. Known allergy to vaccines or vaccines ingredients;
5. Autoimmune diseases, immunodeficiency diseases (including but not limited to systemic lupus erythematosus, ankylosing spondylitis, autoimmune thyroid diseases, asplenia, functional asplenia, and HIV infection);
6. Coagulation disorders (e.g. factor deficiency, platelet disorders), or history of bleeding, hematoma, or bruising following intramuscular injections or venipuncture;
7. Poorly controlled chronic illnesses or history of severe diseases that, including but not limited to cardiovascular diseases, hematological disorders, liver and kidney diseases, digestive system disorders, respiratory diseases, malignancies, and a history of major organ transplantation;
8. Current or history of severe neurological diseases \[epilepsy, convulsions or seizures (excluding history of febrile seizures)\] or psychiatric disorders, or presence of a family history of psychiatric disorders;
9. Receipt of ≥14 days of immunosuppressive or other immunomodulatory therapy (prednisone ≥20mg/day, or prednisone ≥2mg/kg/day, or its equivalent), cytotoxic therapy within 180 days prior to screening, or plans for such treatment during the trial;
10. Receipt of blood products or immunoglobulins within 180 days prior to screening, or plans to receive these treatments in the trial;
11. Receipt of other investigational drugs/vaccines within 30 days prior to screening, or plans to receive such drugs or vaccines during the study period;
12. Receipt of attenuated live vaccines or nucleic acid vaccines within 14 days prior to screening, or subunit or inactivated vaccines within 7 days prior to screening;
13. Fever on vaccination day, with axillary temperature \>37.2°C pre-vaccination, or vital signs outside normal range, or failure to pass physical examination;
14. Presence of skin injuries, inflammation, ulcers, rashes, scars, or other conditions at the intended injection site that may interfere with drug administration or observation of local reactions;
15. Acute onset of various acute diseases or chronic diseases within the past 7 days, or known or suspected active infections;
16. Any other factors considered by the investigator to make the participant unsuitable for participation in the trial.