Inclusion Criteria:  Age ≥ 18 years old, Through asking medical history and physical examination, the investigator judged that the health condition is good: the chronic disease is stable and there is no change within 3 months of medication; has been completed 2 doses of Covid-19 Inactivated vaccine 4-8 months ago; Female participants of childbearing age who were not breast-feeding or pregnant (negative blood pregnancy test), and had no family planning in the first 3 months after enrollment and took effective contraceptive measures. Take effective contraceptive measures within 2 weeks before inclusion; Volunteered to receive the third dose of vaccine.And during the entire follow-up research period, be able and willing to complete the entire prescribed research plan; Have the ability to self-understand research procedures, informed consent & voluntarily sign informed consent, and be able to comply with the requirements of the plan  Exclusion Criteria:  RT-qPCR detects active SARS-Cov-2 infection; a history of COVID-19, SARS, MERS infection (self-report, on-site inquiry); a high-risk factor for COVID-19 infection: a history of close contact with people infected with the new coronavirus, a history of living in high-risk areas, and a history of contact with patients with fever or respiratory symptoms in high-risk areas or abroad. Fever, dry cough, fatigue, nasal congestion, runny nose, sore throat, myalgia, diarrhea, shortness of breath, dyspnea, etc. 7 days before enrollment; receiving COVID-19 booster vaccination; allergic to the active ingredients of the SARS-CoV-2 vaccine, any of the inactive ingredients, the substances used in the production process, or those who have had allergies during previous vaccination of similar vaccines; those who have had severe allergic reactions to vaccines in the past (such as acute allergic reactions, angioedema, respiratory Difficulties, urticaria, angioedema or abdominal pain); body temperature >37.0℃ before vaccination; blood pregnancy test positive; with uncontrolled epilepsy and other serious neurological diseases (such as transmissive myelitis, Guillain-Barre syndrome) , Demyelinating diseases, etc.), or have a history or family history of encephalopathy or mental disease; severe liver and kidney disease, uncontrollable hypertension (systolic blood pressure ≥180 mmHg, diastolic blood pressure ≥100 mmHg), diabetic complications, Malignant tumors, various acute diseases or acute attacks of chronic diseases; diagnosed with congenital or acquired immunodeficiency, HIV infection, lymphoma, leukemia or other autoimmune diseases; receiving anti-tuberculosis treatment; a history of coagulopathy ( Such as coagulation factor deficiency, coagulation disease) within 3 months of subjects receiving immunotherapy or inhibitor therapy (continuous oral or infusion for more than 14 days), or after 3 months of hormone therapy, the average daily dose is ≥20mg/day (Prednisone); Receiving live attenuated vaccine within 1 month before this vaccination, other vaccines within 14 days before this vaccination; Receiving other research drugs within 3 months before vaccination; participating in other research vaccines Or subjects in clinical trials of research drugs; other conditions that the investigator judges are not suitable for this clinical trial;