Known allergy to (components of) the BCG vaccine or serious adverse events to prior BCG administration, Known active or latent infection with Mycobacterium tuberculosis (M. tuberculosis) or other mycobacterial species, Previous M. tuberculosis infection, Previous confirmed COVID-19 infection, Fever (>38 C) within the past 24 hours, Suspicion of active viral or bacterial infection, Pregnancy, Breastfeeding, Vaccination with other live attenuated vaccine within the last 4 weeks, Severely immunocompromised subjects. This exclusion category comprises a) subjects with known infection by the human immunodeficiency virus (HIV-1), b) subjects with solid organ transplantation, c) subjects with bone marrow transplantation, d) subjects under chemotherapy, e) subjects with primary immunodeficiency, f) treatment with any anti-cytokine therapies. g) treatment with oral or intravenous steroids defined as daily doses of 10 mg prednisone or equivalent for longer than 3 months, Active solid or non-solid malignancy or lymphoma within the prior two years, Direct involvement in the design or the execution of the BCG-DENMARK-COVID study, Employed to the hospital < 22 hours per week.

Known allergy to (components of) the BCG vaccine or serious adverse events to prior BCG administration, Known active or latent infection with Mycobacterium tuberculosis (M. tuberculosis) or other mycobacterial species, Previous M. tuberculosis infection, Previous confirmed COVID-19 infection, Fever (>38 C) within the past 24 hours, Suspicion of active viral or bacterial infection, Pregnancy, Breastfeeding, Vaccination with other live attenuated vaccine within the last 4 weeks, Severely immunocompromised subjects. This exclusion category comprises a) subjects with known infection by the human immunodeficiency virus (HIV-1), b) subjects with solid organ transplantation, c) subjects with bone marrow transplantation, d) subjects under chemotherapy, e) subjects with primary immunodeficiency, f) treatment with any anti-cytokine therapies. g) treatment with oral or intravenous steroids defined as daily doses of 10 mg prednisone or equivalent for longer than 3 months, Active solid or non-solid malignancy or lymphoma within the prior two years, Direct involvement in the design or the execution of the BCG-DENMARK-COVID study, Employed to the hospital < 22 hours per week.