COVID-19 death and BCG vaccination programs worldwide

Several clinical trials are being conducted worldwide to investigate the protective effect of Bacillus Calmette-Guérin (BCG) vaccine against death in healthcare providers who are working directly with coronavirus disease 2019 (COVID-19) patients. Clinical studies suggested that certain live vaccines, particularly BCG vaccine, could reduce the mortality due to other diseases caused by non-targeted pathogens, most probably through what is known as non-specific effects (heterologous effects). The most recent available information on the COVID-19 pandemic indicated the great effect of BCG vaccine in reducing the number of COVID-19 death cases. The occurrence of death due to COVID-19 was found to be 21-fold lower in countries with a national BCG vaccination policy than in countries without such a policy, based on the medians of COVID-19 death case per 1 million of population in these two groups of countries (P<0.0001, Mann-Whitney test). Therefore, it can be concluded that the early establishment of BCG vaccination policy in any country is a key element in reducing the number of COVID-19 and tuberculosis death cases.