Before revision:  Accordingly, it has been hypothesized that it may have a protective effect against COVID-19. 12 randomized controlled trials are currently underway to test this hypothesis, but their results shall not be available before at least five months.
After revision:  Accordingly, it has been hypothesized that it may have a protective effect against COVID-19. Recent research found that countries with universal Bacillus Calmette-Gu\'erin (BCG) childhood vaccination policies tend to be less affected by the COVID-19 pandemic. However, such ecological studies are biased by numerous confounders.