immunogenicity and safety of covid-19 vaccine , inactivated co -administration with ev71 vaccine (vero cell)

Conditions: COVID-19

Summary: this study is a randomized and controlled phase ⅳ clinical trial of the covid-19 vaccine (vero cell), inactivated manufactured by sinovac research \& development co., ltd. the purpose of this study is to evaluate the immunogenicity and safety of covid-19 vaccine (vero cell), inactivated co-administration with ev71 vaccine

this study is a randomized and controlled phase ⅳ clinical trial in children aged 3-5 years old. the purpose of this study is to evaluate the immunogenicity and safety of covid-19 vaccine (vero cell), inactivated co-administration with ev71 vaccine.the covid-19 vaccine was manufactured by sinovac research \& development co., ltd, and the ev71 vaccine was manufactured by sinovac biotech co.a total of 520 subjects aged 3-5 years old will be enrolled.subjects will be randomly divided into 2 groups in a ratio of 1:1.the experimental group is the combined immunization group, which will receive the first dose of covid-19 vaccine and the second dose of covid-19 vaccine and ev71 vaccine on day 28;control group is the non-combined immunization group , which will receive the first dose of covid-19 vaccine on day 0 ，the first dose of ev71 vaccine on day 14 ，the second dose of covid-19 vaccine on day 28 and the second dose of ev71 vaccine on day 42.

Eligibility criteria:
inclusion criteria: * children aged 3-5 years ; * the subject and/or guardian can understand and voluntarily sign the informed consent form * proven legal identity; exclusion criteria: * history of contact with a sars-cov-2 infection (positive in nucleic acid test) within 14 days; * history of multiple system inflammatory syndrome (mis-c); * history of hand, foot and mouth disease, herpetic angina or ev71 vaccination; * history of asthma, history of allergy to the vaccine or vaccine components,or serious adverse reactions to the vaccine, such as urticaria, dyspnea,and angioedema; * congenital malformations or developmental disorders, genetic defects,severe malnutrition, etc.; * autoimmune disease (systemic lupus erythematosus)or immunodeficiency / immunosuppression(hiv,history after organ transplantation)； * severe chronic diseases, severe cardiovascular diseases, hypertension and diabetes that cannot be controlled by drugs, liver or kidney diseases,malignant tumors, etc.; * severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; * thyroid disease or history of thyroidectomy, asplenia,functional asplenia, asplenia or splenectomy resulting from any condition; * diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy,abnormal platelets) or obvious bruising or blood coagulation; * immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months; * history of drug abuse; * receipt of blood products within in the past 3 months; * receipt of other investigational drugs in the past 30 days; * receipt of attenuated live vaccines in the past 14 days; * receipt of inactivated or subunit vaccines in the past 7 days; * severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; * axillary temperature \>37.0°c; * the subjects participated in other clinical trials during the follow-up period, or will be planned within 3 months; * according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.