Inclusion criteria:
Age between 18 and 50 years old
Healthy in terms of past medical history, physical examination, and laboratory data-
Body mass index: 17-35 kg/m2
Willingness to participate in the study and complete follow-up
Ability to comprehend study methodology
Ability to comprehend and sign informed consent-
Provision of consent to access medical documents in case of contracting COVID-19
For women: negative pregnancy screening
Acceptance of contraception use from 21 days before randomization until six months after receiving the last vaccine dose
Acceptance of not receiving blood product or bone marrow from randomization until three months after receiving last vaccine dose
Exclusion criteria:
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-