inclusion criteria: * primary contacts, described below, aged 18 to 65 years and having provide written informed consent by the patient, by the patient's legal /authorized representative as applicable. according to below criteria, as soon as a new subject in identified, he/she will be consented for reaching his contacts according to below criteria. the research team within 48 hours of index case identification will call his/her contacts who fulfill below criteria for participation in the trial. all potential participants will be tested using rt-pcr and igm and igg antibodies to rule out current or previous disease status. contact is a person free from covid-19 who experienced any one of the following exposures during the 2 days before and the 14 days after the onset of symptoms of a probable or confirmed case: * a person living in the same household as a covid-19 case * a person having had direct physical contact with a covid-19 case (e.g. shaking hands) * a person having unprotected direct contact with infectious secretions of a covid-19 case (e.g. being coughed on, touching used paper tissues with a bare hand) * a person having had face-to-face contact with a covid-19 case within 2 meters \[2\] and \> 15 minutes * a person who was in a closed environment (e.g. classroom, meeting room, hospital waiting room, etc.) with a covid-19 case for 15 minutes or more and at a distance of less than 2 meters * a healthcare worker (hcw) or other person providing direct care for a covid-19 case, or laboratory workers handling specimens from a covid-19 case without recommended personal protective equipment or with a possible breach of personal protective equipment use policies * a contact in an aircraft sitting within two seats (in any direction) of the covid-19 case, travel companions or persons providing care, and crew members serving in the section of the aircraft where the index case was seated (if severity of symptoms or movement of the case indicate more extensive exposure, passengers seated in the entire section or all passengers on the aircraft may be considered close contacts)

inclusion criteria: * primary contacts, described below, aged 18 to 65 years and having provide written informed consent by the patient, by the patient's legal /authorized representative as applicable. according to below criteria, as soon as a new subject in identified, he/she will be consented for reaching his contacts according to below criteria. the research team within 48 hours of index case identification will call his/her contacts who fulfill below criteria for participation in the trial. all potential participants will be tested using rt-pcr and igm and igg antibodies to rule out current or previous disease status. contact is a person free from covid-19 who experienced any one of the following exposures during the 2 days before and the 14 days after the onset of symptoms of a probable or confirmed case: * a person living in the same household as a covid-19 case * a person having had direct physical contact with a covid-19 case (e.g. shaking hands) * a person having unprotected direct contact with infectious secretions of a covid-19 case (e.g. being coughed on, touching used paper tissues with a bare hand) * a person having had face-to-face contact with a covid-19 case within 2 meters \[2\] and \> 15 minutes * a person who was in a closed environment (e.g. classroom, meeting room, hospital waiting room, etc.) with a covid-19 case for 15 minutes or more and at a distance of less than 2 meters * a healthcare worker (hcw) or other person providing direct care for a covid-19 case, or laboratory workers handling specimens from a covid-19 case without recommended personal protective equipment or with a possible breach of personal protective equipment use policies * a contact in an aircraft sitting within two seats (in any direction) of the covid-19 case, travel companions or persons providing care, and crew members serving in the section of the aircraft where the index case was seated (if severity of symptoms or movement of the case indicate more extensive exposure, passengers seated in the entire section or all passengers on the aircraft may be considered close contacts)

inclusion criteria: - primary contacts, described below, aged 18 to 65 years and having provide written informed consent by the patient, by the patient's legal /authorized representative as applicable. according to below criteria, as soon as a new subject in identified, he/she will be consented for reaching his contacts according to below criteria. the research team within 48 hours of index case identification will call his/her contacts who fulfill below criteria for participation in the trial. all potential participants will be tested using rt-pcr and igm and igg antibodies to rule out current or previous disease status. contact is a person free from covid-19 who experienced any one of the following exposures during the 2 days before and the 14 days after the onset of symptoms of a probable or confirmed case: - a person living in the same household as a covid-19 case - a person having had direct physical contact with a covid-19 case (e.g. shaking hands) - a person having unprotected direct contact with infectious secretions of a covid-19 case (e.g. being coughed on, touching used paper tissues with a bare hand) - a person having had face-to-face contact with a covid-19 case within 2 meters [2] and > 15 minutes - a person who was in a closed environment (e.g. classroom, meeting room, hospital waiting room, etc.) with a covid-19 case for 15 minutes or more and at a distance of less than 2 meters - a healthcare worker (hcw) or other person providing direct care for a covid-19 case, or laboratory workers handling specimens from a covid-19 case without recommended personal protective equipment or with a possible breach of personal protective equipment use policies - a contact in an aircraft sitting within two seats (in any direction) of the covid-19 case, travel companions or persons providing care, and crew members serving in the section of the aircraft where the index case was seated (if severity of symptoms or movement of the case indicate more extensive exposure, passengers seated in the entire section or all passengers on the aircraft may be considered close contacts)

inclusion criteria: - primary contacts, described below, aged 18 to 65 years and having provide written informed consent by the patient, by the patient's legal /authorized representative as applicable. according to below criteria, as soon as a new subject in identified, he/she will be consented for reaching his contacts according to below criteria. the research team within 48 hours of index case identification will call his/her contacts who fulfill below criteria for participation in the trial. all potential participants will be tested using rt-pcr and igm and igg antibodies to rule out current or previous disease status. contact is a person free from covid-19 who experienced any one of the following exposures during the 2 days before and the 14 days after the onset of symptoms of a probable or confirmed case: - a person living in the same household as a covid-19 case - a person having had direct physical contact with a covid-19 case (e.g. shaking hands) - a person having unprotected direct contact with infectious secretions of a covid-19 case (e.g. being coughed on, touching used paper tissues with a bare hand) - a person having had face-to-face contact with a covid-19 case within 2 meters [2] and > 15 minutes - a person who was in a closed environment (e.g. classroom, meeting room, hospital waiting room, etc.) with a covid-19 case for 15 minutes or more and at a distance of less than 2 meters - a healthcare worker (hcw) or other person providing direct care for a covid-19 case, or laboratory workers handling specimens from a covid-19 case without recommended personal protective equipment or with a possible breach of personal protective equipment use policies - a contact in an aircraft sitting within two seats (in any direction) of the covid-19 case, travel companions or persons providing care, and crew members serving in the section of the aircraft where the index case was seated (if severity of symptoms or movement of the case indicate more extensive exposure, passengers seated in the entire section or all passengers on the aircraft may be considered close contacts)