inclusion criteria: * any medical or non-medical personnel of the philippine general hospital and the up manila national institutes of health to include physicians (consultants, fellows-in-training, residents-in-training); nurses and other nursing staff (nursing aide, institutional or utility worker); janitors and cleaning staff, medical technologists and personnel of the laboratory where the covid pcr testing is done; technicians of the radiology department, electrocardiography (ecg) station, arterial blood gas (abg) stations and other personnel employed by the hospital on a tenured, part-time or full-time,and temporary. because of the sample size, there is also a plan to include also health care workers in the community quarantine centers in the manila area such as the rizal coliseum or the ninoy aquino stadium, or at the world trade center * aged 18-59 years * exposure to a probable or confirmed covid19 case within 4 days prior to study enrollment that is considered to be medium or high risk as defined by the hicu * asymptomatic (no acute respiratory, flu-like, gastrointestinal signs and symptoms at the time of enrollment * negative baseline covid19 rt-pcr test result\* * for female participants of child bearing potential they must agree to effective birth control methods during the clinical trial or abstinence from any sexual activity during the duration of the study. * since rt-pcr result may not be released right away, volunteers who test positive after preliminary enrollment will be screen-failed and will not be included in the analysis.

inclusion criteria: * any medical or non-medical personnel of the philippine general hospital and the up manila national institutes of health to include physicians (consultants, fellows-in-training, residents-in-training); nurses and other nursing staff (nursing aide, institutional or utility worker); janitors and cleaning staff, medical technologists and personnel of the laboratory where the covid pcr testing is done; technicians of the radiology department, electrocardiography (ecg) station, arterial blood gas (abg) stations and other personnel employed by the hospital on a tenured, part-time or full-time,and temporary. because of the sample size, there is also a plan to include also health care workers in the community quarantine centers in the manila area such as the rizal coliseum or the ninoy aquino stadium, or at the world trade center * aged 18-59 years * exposure to a probable or confirmed covid19 case within 4 days prior to study enrollment that is considered to be medium or high risk as defined by the hicu * asymptomatic (no acute respiratory, flu-like, gastrointestinal signs and symptoms at the time of enrollment * negative baseline covid19 rt-pcr test result\* * for female participants of child bearing potential they must agree to effective birth control methods during the clinical trial or abstinence from any sexual activity during the duration of the study. * since rt-pcr result may not be released right away, volunteers who test positive after preliminary enrollment will be screen-failed and will not be included in the analysis.

inclusion criteria: - any medical or non-medical personnel of the philippine general hospital and the up manila national institutes of health to include physicians (consultants, fellows-in-training, residents-in-training); nurses and other nursing staff (nursing aide, institutional or utility worker); janitors and cleaning staff, medical technologists and personnel of the laboratory where the covid pcr testing is done; technicians of the radiology department, electrocardiography (ecg) station, arterial blood gas (abg) stations and other personnel employed by the hospital on a tenured, part-time or full-time,and temporary. because of the sample size, there is also a plan to include also health care workers in the community quarantine centers in the manila area such as the rizal coliseum or the ninoy aquino stadium, or at the world trade center - aged 18-59 years - exposure to a probable or confirmed covid19 case within 4 days prior to study enrollment that is considered to be medium or high risk as defined by the hicu - asymptomatic (no acute respiratory, flu-like, gastrointestinal signs and symptoms at the time of enrollment - negative baseline covid19 rt-pcr test result* - for female participants of child bearing potential they must agree to effective birth control methods during the clinical trial or abstinence from any sexual activity during the duration of the study. - since rt-pcr result may not be released right away, volunteers who test positive after preliminary enrollment will be screen-failed and will not be included in the analysis.

inclusion criteria: - any medical or non-medical personnel of the philippine general hospital and the up manila national institutes of health to include physicians (consultants, fellows-in-training, residents-in-training); nurses and other nursing staff (nursing aide, institutional or utility worker); janitors and cleaning staff, medical technologists and personnel of the laboratory where the covid pcr testing is done; technicians of the radiology department, electrocardiography (ecg) station, arterial blood gas (abg) stations and other personnel employed by the hospital on a tenured, part-time or full-time,and temporary. because of the sample size, there is also a plan to include also health care workers in the community quarantine centers in the manila area such as the rizal coliseum or the ninoy aquino stadium, or at the world trade center - aged 18-59 years - exposure to a probable or confirmed covid19 case within 4 days prior to study enrollment that is considered to be medium or high risk as defined by the hicu - asymptomatic (no acute respiratory, flu-like, gastrointestinal signs and symptoms at the time of enrollment - negative baseline covid19 rt-pcr test result* - for female participants of child bearing potential they must agree to effective birth control methods during the clinical trial or abstinence from any sexual activity during the duration of the study. - since rt-pcr result may not be released right away, volunteers who test positive after preliminary enrollment will be screen-failed and will not be included in the analysis.