SA55 Injection Phase II Study in the Treatment of Mild/Moderate COVID-19 Patients

Inclusion Criteria: * Male or female aged ≥ 18 years on the day of enrollment; * On the day of enrollment, novel coronavirus nucleic acid test was positive and/or novel coronavirus antigen test was positive; * On the day of enrollment, it meets the criteria for mild or medium COVID-19 cases, and the time from the first COVID-19 infection related symptoms is within 72 hours; * Within 24 hours before enrollment, one or more of the following symptoms or signs must be present: a. fever, b. cough, c. sore throat, d. nasal congestion/runny nose, e. headache, f. muscle pain, g. shortness of breath/difficulty breathing, h. nausea, i. fatigue, j. vomiting, k. diarrhea; * Subjects (male and female of childbearing age) and their sexual partners voluntarily take effective contraceptive measures within 6 months after signing the informed consent form and administering the experimental drug, and do not have plans to donate sperm or eggs; * At rest, when inhaling air, the oxygen saturation is greater than 93%; * Subjects voluntarily participate in the experiment and sign an informed consent form before the start of the study. Exclusion Criteria: * Individuals who are known to be allergic to the investigational drug, any component in the preparation, or other similar drugs; * Individuals weighing less than 40 kg; * There are comorbidities that require surgery within one month, or comorbidities that are considered life-threatening within one month; * Before screening, he has received neutralizing antibody drugs from COVID-19, or received human immunoglobulin or convalescent plasma treatment from convalescent patients within 3 months, or received small molecule drugs from COVID-19 within 7 days; * Suspected or confirmed to have combined serious and active bacterial, fungal, viral or other infections (except for COVID-19 infection), such as acute systemic infection, the researcher believes that intervention measures may pose a risk; * Individuals who tested positive for influenza A/B virus antigens during screening; * Plan to become pregnant within 6 months, already pregnant, or breastfeeding; * Participated in clinical trials of other drugs or medical devices within 3 months prior to screening; * Having/having suffered from severe neurological disorders (epilepsy, convulsions, or seizures) or mental illness, or having a family history of mental illness; * Suffering from/having previously suffered from severe neurological diseases or other serious illnesses that the researcher has determined to be unsuitable for participation in the study (including but not limited to current systemic infections, uncontrolled autoimmune diseases, uncontrolled immunodeficiency diseases, history of myocardial infarction or heart disease, etc.); * Unable to cooperate with the follow-up of the study, or unable to guarantee the non use of concomitant drugs/vaccines/treatments prohibited by this protocol during the study period (see section 6.4.2); * The researcher believes that due to other reasons, it is not suitable to participate in this study.