TB infection and BCG vaccination: are we protected from COVID-19?

OBJECTIVES: The incidence of emerging coronavirus disease 2019 (COVID-19) disease is variable across the different parts of the world. Apart from travel patterns, other factors determining this difference may include host immune response. The aim of this study was to assess the effect of tuberculosis (TB) endemicity and Bacille Calmette-Guerin (BCG) coverage on COVID-19. STUDY DESIGN: This was a cross-sectional study. METHODS: We reviewed available data regarding TB incidence, BCG coverage (as per the World Health Organization), and COVID-19 incidence of 174 countries. We divided the countries into four cohorts depending on annual TB incidence and BCG coverage. RESULTS: Countries with high TB incidence had lower COVID-19 than countries with low TB incidence. Similarly, countries with high BCG coverage had lower incidence of COVID-19, suggesting some protective mechanisms in TB-endemic areas. However, the ecological differences and different testing strategies between countries could not be accounted for in this analysis. CONCLUSION: Higher TB incidence and BCG coverage were found to be associated with lesser incidence of COVID-19. This outcome paves the way for further research into pathogenesis and immune response in COVID-19.