Ecological studies have suggested fewer COVID-19 morbidities and mortalities in Bacillus Calmette–Guérin (BCG)-vaccinated countries than BCG-non-vaccinated countries. However, these studies obtained data during the early phase of the pandemic and did not adjust for potential confounders, including PCR-test numbers per population (PCR-tests). Currently—more than four months after declaration of the pandemic—the BCG-hypothesis needs reexamining. An ecological study was conducted by obtaining data of 61 factors in 173 countries, including BCG vaccine coverage (%), using morbidity and mortality as outcomes, obtained from open resources. ‘Urban population (%)’ and ‘insufficient physical activity (%)’ in each country was positively associated with morbidity, but not mortality, after adjustment for PCR-tests. On the other hand, recent BCG vaccine coverage (%) was negatively associated with mortality, but not morbidity, even with adjustment for percentage of the population ≥ 60 years of age, morbidity, PCR-tests and other factors. The results of this study generated a hypothesis that a national BCG vaccination program seems to be associated with reduced mortality of COVID-19, although this needs to be further examined and proved by randomized clinical trials.
【저자키워드】 COVID-19, SARS-CoV-2, Coronavirus disease 2019, vaccination, Mortality, morbidity, BCG, Ecological study, urbanization, Bacillus Calmette–Guérin, 【초록키워드】 Vaccine, pandemic, physical activity, outcomes, Coverage, Factors, age, morbidity and mortality, randomized clinical trials, Hypothesis, BCG vaccination, Factor, early phase, confounders, National, Bacillus, resources, country, examined, conducted, reduced, suggested, ecological, adjust,