Dr. Neil Schluger, chief of the division of pulmonary, allergy and critical care medicine at Columbia, and his team studied more than 1,300 patients admitted to New York-Presbyterian Hospital-Columbia University Irving Medical Center for COVID-19. Some received hydroxychloroquine on an off-label basis, a practice that allows doctors to prescribe a drug that has been approved for one disease to treat another — in this case, COVID-19. About 60% of the patients received hydroxychloroquine for about five days. They did not show any lower rate of needing ventilators or a lower risk of dying during the study period compared to people not getting the drug.

“We don’t think at this point, given the totality of evidence, that it is reasonable to routinely give this drug to patients,” says Schluger. “We don’t see the rationale for doing that.” While the study did not randomly assign people to receive the drug or placebo and compare their outcomes, the large number of patients involved suggests the findings are solid.

Based on the results, Schluger says doctors at his hospital have already changed their advice about using hydroxychloroquine to treat COVID-19.