This study is an open-label, single-center, randomized phase IV clinical trial of the SARS-CoV-2 inactivated vaccine manufactured by Sinovac Research & Development Co., Ltd. The purpose of this study is to evaluate the safety and immunogenicity of concomitant administration of the SARS-CoV-2 Inactivated Vaccine (Vero cell) with Quadrivalent Influenza Vaccine in adults aged from 18 to 59 Years

This study is an open-label, single-center, randomized phase IV clinical trial of the SARS-CoV-2 inactivated vaccine (Vero cell) manufactured by Sinovac Research & Development Co., Ltd. The purpose of this study is to evaluate the safety and immunogenicity of concomitant administration of the SARS-CoV-2 Inactivated Vaccine (Vero cell) with Quadrivalent Influenza Vaccine in adults aged from 18 to 59 Years. 480 healthy adults as participants are randomly assigned into two groups in the ratio 1:1. The first group was the combined immunization group, which is randomly divided into two subgroups, 120 subjects in each group. The combined immunization subgroup Ⅰ receive SARS-CoV-2 inactivated vaccine &Quadrivalent Influenza Vaccine on day 0 and SARS-CoV-2 inactivated vaccine (second dose) on day 28.The combined immunization subgroup Ⅱ receive SARS-CoV-2 inactivated vaccine on day 0 and SARS-CoV-2 inactivated vaccine (second dose) & Quadrivalent Influenza Vaccine on day 28. The second group was the non combined immunization group，which receive SARS-CoV-2 inactivated vaccine (first dose) on day 0, Quadrivalent Influenza Vaccine on day 14 and SARS-CoV-2 inactivated vaccine (second dose) on day 28.

Inclusion Criteria:

• Healthy adults aged 18-59 years;
• The subject can understand and voluntarily sign the informed consent form;
• Proven legal identity

Exclusion Criteria:

• Travel history / residence history of communities with case reports within 14 days;

• History of contact with a SARS-CoV-2 infection (positive in nucleic acid test) within 14 days;

• Have contacted patients with fever or respiratory symptoms from communities with case reports within 14 days;

• Two or more cases of fever and / or respiratory symptoms in a small contact area of volunteers, such as home, office etc. within 14 days;

• History of SARS-CoV-2 infection;

• 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 or immunodeficiency / immunosuppression;

• 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, spleenlessness, functional spleenlessness, spleenlessness 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;

• Physical examination has clinically significant abnormal hematology and biochemistry laboratory test results that exceed the reference value range (only applicable to phase I clinical trials):

  1. Blood routine test: white blood cell count, hemoglobin, platelet count;
  2. Detection of blood biochemical indicators: alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), creatinine (CR), fasting blood glucose;
  3. Urine routine index: urine protein (PRO);

• History of alcohol or 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;

• Acute diseases or acute exacerbation of chronic diseases in the past 7 days;

• Axillary temperature >37.0°C;

• Already pregnant (including a positive urine pregnancy test) or are breastfeeding, planning to get pregnant 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.