Researchers at the New York Institute of Technology’s College of Osteopathic Medicine report that a vaccine long used against tuberculosis may mitigate the effects of Covid-19, reducing the fatality rate. The study—preprinted on March 24 and awaiting peer review—offers hope to countries in Latin America. As it turns out, in a region where many people can’t afford to lose income by staying home and public-health systems are weak, there is also a history of administering the Bacillus Calmette-Guérin tuberculosis vaccine to…