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