The Effects of BCG on COVID-19 Mortality

In July, the proceedings of the National Academy of Sciences showed that for every 10% increase in an index of BCG coverage within a country there was a 10.4% decrease in COVID-19 mortality. The population coverage data is tantalizing in the sense that we really don't understand why some of the countries that we expected to see really high COVID death rates in have not yet experienced that. So many countries in Africa have been relatively protected from having high case fatality rates.