This study is a multicenter, randomized, single-blind, placebo-controlled clinical trial to evaluate the effectiveness and safety of Anti-COVID-19 Antibody SA55 for Injection in patients with hematological malignancies. This study consists of two stages. In the first stage, 8 subjects aged 18-75 were recruited for safety assessment, including the monitoring of clinical test indicators and adverse events. After confirming the preliminary safety results of the first stage, we plan to recruit 160 COVID-19 patients with hematologic disorders aged 1-75 years old and randomly divided into the SA55 group and the placebo group with a ratio of 3:1. Basic information and laboratory tests will be collected during the whole study, and the occurrence of adverse events and SAEs of all subjects were collected.

Inclusion Criteria:

Subjects in this study must meet all of the following criteria:

1. Male or female patients with hematological malignancies who are in stable condition or with bone marrow failure disorders and aged from 1 to 75 years old on the day of enrollment;
2. On the day of enrollment, the subject was judged to be positive for Covid-19 nucleic acid/antigen for more than 10 days without turning negative or had turned negative but recovered positive again after 10 days;
3. On the day of enrollment, patients who have received CAR T-cell therapy, corticosteroids for a long time or other immuno-suppressive drugs, with the proportion of peripheral blood B cells is less than 2%;
4. Subjects (men and women with childbearing potential) and their sexual partners voluntarily take effective contraceptive measures from 4 weeks before screening to 3 months after the last dose of the test drug, and have no plan to donate sperm or eggs;
5. Subjects voluntarily participate in the trial and sign the informed consent form before the study begins.

Exclusion Criteria:

Those who meet any of the following conditions will be excluded:

1. Those who are known to be allergic to the test drug and any component in the preparation, or other similar drugs;
2. Complications requiring surgery within 7 days, or complication considered life-threatening within 28 days;
3. Received treatment with SARS-CoV-2 neutralizing antibody drugs before screening;
4. Convalescent plasma from recovered patients before screening;
5. Patients who took anti-SARS-CoV-2 drugs within 48 hours before enrollment, including but not limited to Paxlovid (Nirmatrelvir/Ritonavir), Azvudine, Molnupiravir, etc.
6. On the day of enrollment, meet the diagnostic criteria for severe/critical new coronavirus pneumonia;
7. Suspected to have been combined with active bacteria, fungi, viruses or other infections other than the new coronavirus;
8. Those who plan to become pregnant, are pregnant, or are breastfeeding;
9. Participated in clinical trials of SARS-CoV-2 neutralizing antibody drugs within 180 days before screening or participated in clinical trials of other drugs or medical devices within 4 weeks before screening;
10. Suffering from severe neurological diseases (epilepsy, convulsions or convulsions) or mental illness, with a family history of mental illness;
11. Suffering from other serious diseases that are not controlled, such as severe cardiovascular and cerebrovascular diseases, liver and kidney diseases, endocrine system diseases; or other diseases that the researchers judge are not suitable for participating in the study (such as currently uncontrolled autoimmune diseases, etc. );
12. Other conditions that the researcher believes are not suitable for participating in this study due to various reasons.