Relationship between COVID-19 death toll doubling time and national BCG vaccination policy

In this manuscript, we showed a statistically significant difference of the doubling times of the death toll between the group of countries with national universal Bacillus Calmette-Guerin (BCG) vaccination and the group without it for recent years. Based on a statistical test, the distributions of the doubling time of these two groups were significantly different (p=0.007). Miller et al. reported the relationship between BCG vaccination and mortality for COVID-19 based on deaths per million inhabitants. However, they did not take into account the differences in COVID-19 detection rates among the countries and the epidemic stages of the countries. Therefore we used a doubling time of the death toll as a more stable indicator instead. We also investigated the dependency of the BCG strains. Among the 42 BCG-vaccinated countries, the median doubling time of the eight countries using “Tokyo 172-1” strain at least partially (Japan, Iraq, Malaysia, South Korea, Philippines, Saudi Arabia, Pakistan, and Bangladesh) was 7.2 days, and that of the other 34 vaccinated countries was 5.5 days. Their distributions were also significantly different (p=0.026).