2014 study by Dyall et al. is an in vitro study; clinical trials showed hydroxychloroquine is ineffective against COVID-19 in people
Hydroxychloroquine and chloroquine are chiefly known for their ability to treat malaria, a parasitic infection. They are also used to treat other conditions, such as the autoimmune disease rheumatoid arthritis. However, clinical trials involving thousands of COVID-19 patients to date found that hydroxychloroquine doesn’t improve disease severity or mortality rate in COVID-19 patients. Health authorities recommend against using hydroxychloroquine to treat COVID-19.