BCG vaccination may reduce the risk of a range of infectious diseases, and if so, it could serve as a protective factor against COVID-19. Here, we compared countries that mandated BCG vaccination at least until 2000 with countries that did not. To minimize any systematic effects of reporting biases, we analyzed the rate of the day-by-day increase in both confirmed cases (135 countries) and deaths (134 countries) in the first 30-day period of country-wise outbreaks. The 30-day window was adjusted to begin at the country-wise onset of the pandemic. Linear mixed models revealed a significant...…BCG vaccination may reduce the risk of a range of infectious diseases, and if so, it could serve as a protective factor against COVID-19. Here, we compared countries that mandated BCG vaccination at least until 2000 with countries that did not. To minimize any systematic effects of reporting biases, we analyzed the rate of the day-by-day increase in both confirmed cases (135 countries) and deaths (134 countries) in the first 30-day period of country-wise outbreaks. The 30-day window was adjusted to begin at the country-wise onset of the pandemic. Linear mixed models revealed a significant...WW…