There is ample evidence from in vitro, animal and human studies that the Bacillus Calmette-Guerin (BCG) vaccine epigenetically reprograms innate immunity to provide "off target" protection against pathogens other than mycobacteria. This process has been termed "trained immunity". Although recent ecological studies suggested an association between BCG policies and the frequency or severity of COVID-19 in different countries, the interpretation of these results is challenging. For this reason, a case-control study aiming to test this hypothesis has been initiated in Quebec. Several phase III clinical trials are underway, including one in Canada, to assess the efficacy of BCG against SARS-CoV-2 infection (results expected in 2021). In the past, BCG has been widely used in Canada but current indications are restricted to high-risk individuals and communities experiencing TB outbreaks as well as for the treatment of bladder cancer. The potential implication of BCG as an interim measure to mitigate COVID-19 is the subject of widespread discussion in the scientific community and can be considered for the vulnerable population in Canada. To conclude, BCG vaccination should be placed on the agenda of research funding agencies, scientific advisory committees on immunization and federal/provincial/territorial public health authorities.
Canadian journal of public health = Revue canadienne de sante publique. 2020 Nov 19 [Epub ahead of print]
Philippe De Wals, Dick Menzies, Maziar Divangahi
Département de Médecine sociale et préventive, Université Laval, CRIUCPQ, 2725, Chemin Sainte-Foy, Québec, QC, G1G 4G5, Canada. ., Montreal Chest Institute and Respiratory Epidemiology Unit, McGill University, Montreal, Quebec, Canada., Meakins-Christie Laboratories, Department of Medicine, McGill University Health Centre, Montreal, QC, Canada.