Association of national Bacille Calmette-Guérin vaccination policy with COVID-19 epidemiology: an ecological study in 78 countries

A possible association between national Bacille Calmette-Guerin (BCG) vaccination policy and lower COVID-19 incidence has been suggested in some preprint papers. Using publicly accessible databases, I explored associations of national BCG vaccination policy with COVID-19 epidemiology in 78 countries. Data collection was conducted from April 25 to May 5, 2020. I compared countries that have a current universal BCG vaccination policy (BCG countries), with countries that currently lack such a policy (non-BCG countries). The mixed effect model revealed national BCG policy decreases in the country-specific risk of death by COVID-19, correspond to odds ratio of 0.446 (95% confidence intervals 0.323 - 0.614, P =1×10-5). In BCG countries, the case increase rate was attenuated marginally by 25.4% (95% CI 3.0 to 42.7, P=0.029) as compared with those of the non-BCG countries. Although the protective mechanism of BCG vaccination against COVID-19 remains unknown, further laboratory and clinical research should be warranted.