ination factors, malaria incidence (because COVID-19 susceptibility may be linked to anti-malarial drug use), and the proportion of the population aged over 65 years, explained a substantial part of the variance in COVID-19 case numbers worldwide. This data support the findings by Sala et al. [13] that there is a significant correlation between BCG vaccination and COVID-19 prevalence. Notably, these correlation patterns may change as the pandemic progresses. For example, while the COVID-19 case numbers (per 1 million population