Positive COVID-19 PCR test Positive antibodies against SARS-CoV-2 (IgG, IgM) History of infection with SARS-CoV-2 documented with RT-PCR test Close contact with COVID-19 infected individual in the past 14 days Isolation due to signs and symptoms that are suspicious of COVID-19 Fever (axillary temperature > 37° C), dry cough, fatigue, nasal congestion, rhinorrhea, sore throat, myalgia, diarrhea, dyspnea in the past 14 days Laboratory abnormalities in biochemistry profile, blood, and urine (including urea, creatinine, fasting blood sugar, Na, K, aspartate transaminase, alanine transaminase, alkaline phosphatase, total bilirubin, hemoglobin, leukocyte count, neutrophil count, lymphocyte count, platelet count, urine protein, urine glucose, blood cells in urine) History of severe allergic reactions or allergy to vaccine components (latex) Experience to severe allergic or allergic reactions to components of the recombinant RBD protein vaccine (latex sensitivity) Personal or family history of seizure, epilepsy, encephalopathy, psychiatric disorder Congenital malformations -History of neurologic diseases or seizure (except for febrile seizure at childhood) Growth disorders Genetic disorders Malnutrition Renal or liver abnormalities Uncontrolled hypertension (>140/90 mmHg) Heart failure with NYHA class ≥2 Recent exacerbations of cardiovascular disease include cardiovascular intervention, the addition of new cardiovascular drugs to control symptoms, or unstable angina. Chronic obstructive lung disease with GOLD score ≥2- Asthma Diabetic complications BMI > 35 kg/m2 History of malignancy in the past five years Exacerbation of chronic diseases in the past 7 days Immunodeficiency, lymphoma, leukemia, autoimmune diseases Thyroid disease or history of thyroidectomy without proper control Splenectomy or history of resection of solid organs Coagulation abnormalities Anti-tuberculosis treatment Positive HBSAg Positive HIV Ab Positive HCV Ab Receiving immunosuppressive therapy for 14 consecutive days in the past 3 months or need for such therapy in the following 6 months Receiving any off-label or investigational therapy for COVID-19 Receiving flu vaccine in the past 14 days or other vaccines in the past 4 weeks History of drug or alcohol abuse in the prior year Receiving immunoglobulin or blood products in the prior 3 months Receiving investigational drugs in the past 45 days Planning to receive other vaccines in the next month Severe psychiatric disorders interfering with participation in the trial Women with positive beta-HCG, pregnancy, or during breastfeeding, or plan to become pregnant during the study High risk occupation for COVID-19 exposure (health care workers) or with decision of investigators First degree family members of the trial personnel Any other reason that the investigators document making volunteers ineligible-

Positive COVID-19 PCR test Positive antibodies against SARS-CoV-2 (IgG, IgM) History of infection with SARS-CoV-2 documented with RT-PCR test Close contact with COVID-19 infected individual in the past 14 days Isolation due to signs and symptoms that are suspicious of COVID-19 Fever (axillary temperature > 37° C), dry cough, fatigue, nasal congestion, rhinorrhea, sore throat, myalgia, diarrhea, dyspnea in the past 14 days Laboratory abnormalities in biochemistry profile, blood, and urine (including urea, creatinine, fasting blood sugar, Na, K, aspartate transaminase, alanine transaminase, alkaline phosphatase, total bilirubin, hemoglobin, leukocyte count, neutrophil count, lymphocyte count, platelet count, urine protein, urine glucose, blood cells in urine) History of severe allergic reactions or allergy to vaccine components (latex) Experience to severe allergic or allergic reactions to components of the recombinant RBD protein vaccine (latex sensitivity) Personal or family history of seizure, epilepsy, encephalopathy, psychiatric disorder Congenital malformations -History of neurologic diseases or seizure (except for febrile seizure at childhood) Growth disorders Genetic disorders Malnutrition Renal or liver abnormalities Uncontrolled hypertension (>140/90 mmHg) Heart failure with NYHA class ≥2 Recent exacerbations of cardiovascular disease include cardiovascular intervention, the addition of new cardiovascular drugs to control symptoms, or unstable angina. Chronic obstructive lung disease with GOLD score ≥2- Asthma Diabetic complications BMI > 35 kg/m2 History of malignancy in the past five years Exacerbation of chronic diseases in the past 7 days Immunodeficiency, lymphoma, leukemia, autoimmune diseases Thyroid disease or history of thyroidectomy without proper control Splenectomy or history of resection of solid organs Coagulation abnormalities Anti-tuberculosis treatment Positive HBSAg Positive HIV Ab Positive HCV Ab Receiving immunosuppressive therapy for 14 consecutive days in the past 3 months or need for such therapy in the following 6 months Receiving any off-label or investigational therapy for COVID-19 Receiving flu vaccine in the past 14 days or other vaccines in the past 4 weeks History of drug or alcohol abuse in the prior year Receiving immunoglobulin or blood products in the prior 3 months Receiving investigational drugs in the past 45 days Planning to receive other vaccines in the next month Severe psychiatric disorders interfering with participation in the trial Women with positive beta-HCG, pregnancy, or during breastfeeding, or plan to become pregnant during the study High risk occupation for COVID-19 exposure (health care workers) or with decision of investigators First degree family members of the trial personnel Any other reason that the investigators document making volunteers ineligible-