Is Bacille Calmette-Guerin (BCG) vaccination protective
against SARS-CoV-2?
BCG vaccination induces metabolic and epigenetic modifications by
enhancing trained immunity (innate immunity to subsequent infections).
It was hypothesized that general BCG vaccination policies adopted by
different countries might have impacted the transmission patterns and/or
COVID-19-associated morbidity and mortality.84,85 BCG
vaccination in childhood was not protective against SARS-CoV-2 infection
in an Israeli cohort.86 In contrast, randomized
controlled trials of BCG-Danish indicated immunomodulation against
pre-COVID-19 respiratory infections with fewer deaths from sepsis and
pneumonia. Two clinical Danish trials of BCG-Danish (BRACE and
BCG-CORONA) are evaluating its impact on healthcare workers as pertains
to COVID-19 infection and severity.87,88