Fig. 4.

COVID-19 morbidity and mortality vs BCG immunization in “old” countries. a, b Total COVID-19 cases and deaths per million against BCG immunization rates for high median age (“old”) countries and regions (n = 61). r and p are from Pearson’s correlation coefficient analysis. c, d Boxplots of total COVID-19 cases and deaths per million “old” all countries in the world (n = 61), grouped by BCG vaccination rate of either < 50% (“No BCG”) or ≥ 50% (BCG). p values indicate the levels of difference between the two groups by two-tailed Student’s t test