Debate on Bacille Calmette-Guérin vaccination against COVID-19: Is it worth performing clinical trials?

The non-specific beneficial effects of Bacille Calmette-Guérin (BCG) vaccination suggest that this vaccine might play a role in protecting individuals against severe coronavirus disease 2019 (COVID-19). Several studies propose that BCG vaccination may increase the body's immunity, thereby preventing respiratory infections caused by other respiratory pathogens. As the number of deaths due to COVID-19 is increasing rapidly and there is no specific treatment available to date, scientists are evaluating the effectiveness of already approved drugs as therapies against COVID-19, and the results were found to vary widely: from no significant effect being observed to a reduction in the time taken for clinical improvement. This study thus aims to evaluate whether it is worth performing clinical trials to examine the effects of the BCG vaccine on COVID-19. We herein emphasize the need to conduct phase III randomized controlled trials with adequate sample size and quality to investigate the effects of the BCG vaccine on COVID-19. In the event that BCG vaccination provides non-specific protection against COVID-19, administering it could be helpful in controlling the transmission of COVID-19 and other infectious diseases during future pandemics.