PARTICIPANTS AND ELIGIBILITY CRITERIA
BCG VACCINE
Potential participants’ eligibility was ascertained during a baseline visit. Exclusion criteria included: previous positive SARS-CoV-2 test; contraindication to BCG vaccine; vaccination with: BCG within the last year, any other live-attenuated vaccine within the last month or any COVID-specific vaccine; and involvement in another COVID-19 prevention trial. All participants had blood samples at baseline for SARS-CoV-2 serology, and those in Brazil also had a baseline SARS-CoV-2 respiratory swab PCR taken. Ethics committee approval was obtained at each site and all participants provided written informed consent.