Hydroxychloroquine was not effective in preventing healthy people from contracting COVID-19 in a randomized clinical trial at the University of Minnesota Medical School. The study tested the drug’s potential as a preventive measure, but was shown to be no more effective than the placebo.

The antimalarial drug has been touted by President Donald Trump as a “game changer” for treating the disease. Trump himself said on May 18 that he was taking the drug to protect against the novel coronavirus, despite a lack of evidence that it would provide the desired effect. Federal regulators have warned of the dangers of taking hydroxychloroquine, including heart problems and death, and have said that the drug should only be taken by hospitalized patients and those participating in clinical trials.