The goal of this clinical trial is to evaluate the immunogenicity of simultaneous administration of varicella live attenuated vaccine (varicella vaccine hereafter) and trivalent inactivated influenza vaccine (TIV hereafter). It will also evaluate the safety of simultaneous administration of the two vaccines. The main questions it aims to answer are:

• If geometric mean titer (GMT) of varicella zoster vrius (VZV) antibody in the simultaneous administration group is non-inferior to that in the varicella vaccine separate group.
• If GMT of hemagglutination inhibition (HI hereafter) antibody in the simultaneous administration group is non-inferior to that in the TIV separate group.

Participants in the simultaneous administration group received a single dose of varicella vaccine and TIV simultaneously on day 0. Participants in the separate groups received a single dose of varicella vaccine or TIV on day 0, respectively.

Inclusion Criteria:

• Healthy children aged 7-12 years;
• 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:

• Vaccination history of varicella vaccine;
• Had received a single dose of influenza vaccine for 2024-2025 season;
• 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.