Immunogenicity and Safety of an Inactivated SARS-CoV-2 Vaccine Coadministered With Two Attenuated Vaccines

Inclusion Criteria: * Aged 4 years old * With legal guardian signing the informed consent * Able to participate in all planned visits and comply with all research procedures (such as completing diary cards of adverse events and participating visits) * With clear vaccination records including no SARS-CoV-2 vaccine history, with 1 varicella vaccine and 2 measles-containing vaccines history * the last attenuated vaccine was administered ≥28 days ago, and other vaccines administered ≥14 days ago * With an axillary temperature ≤37.5℃ at the time of vaccination Exclusion Criteria: First dose exclusion criteria: * With SARS-CoV-2 infection in the last 3 months (any of the following conditions shall be met: positive nucleic acid test; positive antigen test; suspected SARS-CoV-2 infection symptoms of subject or close contacts) * allergic to any substance of the vaccine or with a severe allergic reactions history of vaccines (such as acute allergic reactions, angioneurotic edema, breathing difficulties, etc.) * Suffering uncontrolled epilepsy or progressive nerve system diseases, or with a history of Gribali syndrome * With acute illness, severe or acute attack of chronic illness or fever * With immunodeficiency or weakened immune system or being treated with immunosuppressant drugs (oral steroids) * Received non specific immunoglobulin within 3 months * Any situation that researchers thought that might influence the consequence of the clinical trial Second dose exclusion criteria： * Occurrence of any serious adverse event that may be related to the previous dose of study vaccine * Occurrence of systemic adverse reactions or allergic reactions with a severity level ≥ 3 recognized by researchers after vaccination * Any new situations that fit the first dose exclusion criteria * Any situation that researchers thought that might influence the consequence of the clinical trial