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| - COVID-19 started in Hubei province in China and has spread to 210 countries within 3 months. The statistic of COVID-19 across the world is reported daily, providing a dynamic perspective for each country. We tested the hypothesis that the vaccination against tuberculosis with BCG correlates with better outcomes for COVID-19 patients. To this end, we combined the information on demography, economy, major chronic diseases, and immunization policies with the COVID-19 outcomes. We filtered out at a fixed date all countries that were below a predetermined value for population size and number of COVID-19 deaths per million (DPM). Altogether, 55 countries, covering 62.9% of the world population, met our criteria and were analyzed. To allow a reliable comparison between countries, each was aligned to a critical alignment threshold date (0.5 DPM). We found that the years of BCG admission are negatively correlated with DPM at varying times post alignment. Results from multivariable regression tests with 22 quantitative properties of each country and its population substantiate the dominant contribution of BCG admission years to the COVID-19 outcomes. Analyzing countries according to an age group partition across several time-points, reveals that the strongest correlation is attributed to the coverage in BCG vaccination of the young population (<25 years), to a lesser degree the middle age group (25-64 years), while BCG coverage status of the elderly (>65 years) was insignificant. More specifically, the signal is attributed to recent immunizations (last 15 years) rather than past policies. We propose that BCG immunization coverage, especially among the most recently vaccinated, may contribute to attenuation of the COVID-19 spread and severity.
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