inclusion criteria: to be included in the trial the participant must: 1. have given written informed consent to participate 2. be aged 18 years to 70 years 3. not previously have been diagnosed with covid-19 4. work in a high-risk secondary or tertiary healthcare setting (hospitals accepting covid-19 patients) with direct patient-facing care

inclusion criteria: to be included in the trial the participant must: 1. have given written informed consent to participate 2. be aged 18 years to 70 years 3. not previously have been diagnosed with covid-19 4. work in a high-risk secondary or tertiary healthcare setting (hospitals accepting covid-19 patients) with direct patient-facing care

inclusion criteria: to be included in the trial the participant must: have given written informed consent to participate be aged 18 years to 70 years not previously have been diagnosed with covid-19 work in a high-risk secondary or tertiary healthcare setting (hospitals accepting covid-19 patients) with direct patient-facing care

inclusion criteria: to be included in the trial the participant must: have given written informed consent to participate be aged 18 years to 70 years not previously have been diagnosed with covid-19 work in a high-risk secondary or tertiary healthcare setting (hospitals accepting covid-19 patients) with direct patient-facing care

inclusion criteria: to be included in the trial the participant must: 1. have given written informed consent to participate 2. be aged 18 years to 70 years 3. not previously have been diagnosed with covid-19 4. work in a high-risk secondary or tertiary healthcare setting (hospitals accepting covid-19 patients) with direct patient-facing care

inclusion criteria: to be included in the trial the participant must: 1. have given written informed consent to participate 2. be aged 18 years to 70 years 3. not previously have been diagnosed with covid-19 4. work in a high-risk secondary or tertiary healthcare setting (hospitals accepting covid-19 patients) with direct patient-facing care