Prevention of COVID-19 Infection to Severe Pneumonia or ARDS

Inclusion Criteria: * Subjects must meet all of the following criteria: 1. Male or female ≥18 years old 2. Subjects with confirmed diagnoses of pneumonia caused by COVID-19 from: * RT-PCR or Abbott ID Now COVID-19 test * Chest X-ray or computed tomography (CT) scan (findings of the increased opacity on a chest X-ray, ground-glass opacity indicative of pneumonia on CT, opinion on consolidation, etc.) 3. Those who can tolerate oral administration 4. Those who do not need oxygen therapy or only need low-flow oxygen (at least 4L/min) but not requiring high-flow oxygen (higher than 4-6L/min) or non-invasive/invasive ventilation primarily according to the WHO guidance 5. Those who are planned to be hospitalized or who are just hospitalized 6. Those who have been fully explained about this clinical study and have voluntarily agreed to participate in this clinical study by signing the informed consent form (ICF) Exclusion Criteria: * Subjects cannot participate in this clinical study if they satisfy any of the following criteria: 1. Those who are diagnosed with viral pneumonia caused by other than COVID-19 or bacterial pneumonia during the screening 2. Patients with severe pneumonia according to the WHO guidance * Have fever or signs of respiratory infections and * Satisfy any one of the following conditions: Respiratory rate \> 30 breaths/min, severe respiratory distress, or room air oxygen saturation (SpO2) ≤ 93% 3. Patients with ARDS according to the WHO guidance 4. Those who have past medical histories described below: * Those who have medical histories of human immunodeficiency virus (HIV), acquired immunodeficiency syndrome (AIDS), or hepatitis B or C viral infection * Those who cannot have a CT test done due to allergy to contrast agents, etc. 5. Those who have comorbidities/symptoms described below: * Those who have a history or evidence of another clinically significant condition that may pose risks to patient safety or interfere with the study procedures, assessments or completion as determined by the investigator * Those who have moderate or severe renal impairment (eGFR \< 60 mL/min/1.73 m2) * Those who have moderate or severe hepatic impairment (Child-Pugh B or C, respectively) 6. Patients who are being treated with corticosteroids or other immunosuppressants for asthma or autoimmune diseases at the entry of study are excluded, because these drugs counteract the action mechanism of EC-18 (PLAG). 7. Those who have any abnormalities in laboratory tests described below: * Clinically significant liver function abnormality (Satisfy any one or more of the following): * Serum alanine aminotransferase (ALT) ≥ upper limit of normal (ULN) × 2.5 * Serum aspartate aminotransferase (AST) ≥ ULN × 2.5 * Serum total bilirubin ≥ ULN × 2.5 8. Patients with uncontrolled diabetes (HbA1c \> 7.0%) 9. Those who have hypersensitivity reactions to the IP and its components 10. Those who satisfy any of the descriptions below: * Pregnant or breastfeeding female subjects * Those who are planning on pregnancy or not using accepted contraception measures during the clinical study 11. Those who have participated in other clinical studies to receive IPs or apply investigational medical devices within 1 month from the time of obtaining the informed consent 12. Those who are considered to be ineligible to participate in the clinical study or have difficulty conducting this clinical study by the investigator 13. Those subjects with Hb \< lower limit of normal (LLN) for males and females 14. Those subjects with a platelet count \< LLN 15. Those subjects with a WBC \< LLN