The goal of this clinical trial is to evaluate the immunogenicity and safety of booster immunization of varicella live attenuated vaccine (varicella vaccine hereafter) at different intervals.

Inclusion Criteria:

• Healthy children aged 7-12 years;
• Has previously received a single dose of varicella vaccine, with at least 3 months since the first dose;
• The subject or legal guardian can understand and sign the informed consent form (double signature is required for those over 8 years old);
• Participants and their legal guardians voluntarily participate in the study and are able to comply with all study procedures;
• Provide legal identity proof;

Exclusion Criteria:

• History of varicella;
• History of severe allergic reactions to vaccines (such as acute anaphylaxis, angioedema, dyspnea, etc.);
• Suffering from acute disease, severe chronic disease, acute exacerbation of chronic disease;
• With any confirmed or suspected immunodeficiency disease, immunocompromised or receiving immunosuppressive therapy (including systemic steroid therapy);
• With a history of congenital immune diseases or close contact with family members with a history of congenital immune diseases;
• With encephalopathy, uncontrolled epilepsy, other progressive neurological disorders, history of Guillain-Barre syndrome;
• Body temperature >37℃ at the time of vaccination;
• Receipt of blood products within 3 months before receiving investigational vaccine;
• Receipt of another study drug within 30 days before receipt of the investigational vaccine;
• Receipt of live attenuated vaccine within 28 days before receipt of investigational vaccine;
• Receipt of subunit or inactivated vaccine within 7 days before receipt of investigational vaccine;
• Participated in other clinical trials before enrollment and were enrolled in another clinical trial during the follow-up period or planned to participate in another clinical trial within 3 months;
• The participant had any other factors that were ineligible for vaccination by in the investigator's judgment.