Using BCG vaccine to enhance non-specific protection of health care workers during the COVID-19 pandemic: A structured summary of a study protocol for a randomised controlled trial in Denmark

The Bacille Calmette-Guérin (BCG) vaccine against tuberculosis is associated with non- specific protective effects against other infections, and significant reductions in all-cause morbidity and mortality have been reported. We aim to test whether BCG vaccination may reduce susceptibility to and/or the severity of COVID-19 and other infectious diseases in health care workers (HCW) and thus prevent work absenteeism.The primary objective is to reduce absenteeism due to illness among HCW during the COVID-19 pandemic. The secondary objectives are to reduce the number of HCW that are infected with SARS-CoV-2, and to reduce the number of hospital admissions among HCW during the COVID-19 pandemic. BCG vaccination of HCW will reduce absenteeism by 20% over a period of 6 months. Placebo-controlled, single-blinded, randomised controlled trial, recruiting study participants at several geographic locations. The BCG vaccine is used in this study on a different indication than the one it has been approved for by the Danish Medicines Agency, therefore this is classified as a phase III study. The trial will recruit 1,500 HCW at Danish hospitals.To be eligible for participation, a subject must meet the following criteria: Adult (≥18 years); Hospital personnel working at a participating hospital for more than 22 hours per week.A potential subject who meets any of the following criteria will be excluded from participation in this study: Known allergy to components of the BCG vaccine or serious adverse events to prior BCG administration Known prior active or latent infection with Mycobacterium tuberculosis (M. tuberculosis) or other mycobacterial species Previous confirmed COVID-19 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) subjects under treatment with any anti-cytokine therapy within the last year g) subjects under treatment with oral or intravenous steroids defined as daily doses of 10 mg prednisone or equivalent for longer than 3 months h) Active solid or non-solid malignancy or lymphoma within the prior two years Direct invo