https://blogs.scientificamerican.com/observations/bad-medicine-is-worse-than-no-medicine/

At a restaurant industry executive event a little while ago, President Donald Trump stated that he was taking hydroxychloroquine or “the hydroxy” as he called it, in an effort to prevent COVID-19 infection. He also said many frontline workers—presumably referring to nurses, doctors and emergency medical technicians—were also taking the drug.

Over the last few months while working in the intensive care unit, I have seen the devastating effects of COVID-19 infection on both the young and the old, on those with no prior medical problems and those with preexisting conditions. But as a critical care doctor taking care of critically ill COVID-19 patients, I do not know anyone who’s taking hydroxychloroquine to reduce the likelihood of catching COVID-19, and I would certainly not recommend it at this point.