The analysis method described in this protocol is a novel simple plausible immunological approach which is non-invasive, high throughput, real-time quantitative monitoring of metabolic activity (MA) profiles of fresh Peripheral Blood Mononuclear Cells (PBMC) in response to various reagents at different concentrations. The purpose of this study is to evaluate the T cells reactivity to SARS COV 2 immunogenic selected peptides by Metabolic Activity Method in convalesce and healthy individuals and to compare it with Antibody response (ELISA) and clinical information

This is a prospective, four groups, open, comparative, controlled study. A total of 400 completed, evaluated subjects will be enrolled in this study. Main Study Measures: Reactivity of T cells to selected SARS COV-2 peptides by MA test and IgG Antibody response to SARS COV-2 by commercial ELISA test.

Study Procedures:

• Screening
• Informed consent signing
• Medical history review
• Blood collection.
• MA test and ELISA test will be performed at Savicell's Laboratory site.

Inclusion Criteria:

• All recruited subjects are between 18 to 90 years old.
• All recruited subjects read the informed consent and then signed the informed consent.
• All recruited subjects filled out the questionnaire form

Exclusion Criteria:

• Subject has active infection or inflammation determined clinically at screening.
• Subject is currently treated with concomitant medication related directly or can affect the immune system as steroids.
• Subject has impaired judgment.
• Known positive HIV, hepatitis B, or hepatitis C, autoimmune disease.
• Known history of a significant medical disorder, which in the investigators' judgment contraindicates the patient's participation.
• Drug or alcohol abuse
• Subject is participating in any other clinical trial for drug investigation within 10 days prior sample collection

Group 1 :COVID -19 convalesce individuals that tested positive to COVID -19 by swab PCR test who were severe/acute/moderate - ill with hospitalization/drug treatment/ breathing support and who have passed one months or more since recovering from COVID-19 illness Group 2:Belong to family members who shared a household with donors in group 1 and were exposed at the time of symptomatic disease, without any diagnoses of COVID-19 and tested PCR negative to COVID-19. Group 3:COVID - 19 convalesce individuals that tested positive to COVID -19 by swab PCR test who were mild or asymptomatic and who have passed more than two weeks since recovering from illness. Group 4:COVID - 19 healthy blood donors that keep rules of social distance and wearing a mask.