Inclusion Criteria:  Have not received any COVID-19 vaccine in the past or at least one dose of CoronaVac manufactured by Sinovac Research and Development Co.,Ltd; Population aged 3~17 years ; The subjects can understand and voluntarily sign the informed consent form and participate in the follow-up;  Exclusion Criteria:  History of severe allergy to the vaccine such as acute allergic reaction,angioedema and dyspnea ; Severe neurological disease such as Myelitis transverse,Guillain-Barre Syndrome and demyelinating disorders; Acute disease,acute onset of chronic disease and severe chronic diseases.