1. COVID-19 incidence [ Time Frame: Measured over the 6 months following randomization]2. Number of participants with asymptomatic or mild COVID-19 disease defined asI. fever (using a self-reported questionnaire); plusII. at least one sign or symptom of respiratory disease including cough; runny/blocked nose (using self-reported questionnaire); plusIII. positive SARS-Cov-2 test (PCR or serology)

1. COVID-19 incidence [ Time Frame: Measured over the 6 months following randomization]2. Number of participants with asymptomatic or mild COVID-19 disease defined asI. fever (using a self-reported questionnaire); plusII. at least one sign or symptom of respiratory disease including cough; runny/blocked nose (using self-reported questionnaire); plusIII. positive SARS-Cov-2 test (PCR or serology)