Since this early study, many more experts have voiced their concerns, including the Food and Drug Administration, which cautioned against using chloroquine or hydroxychloroquine outside of a hospital or clinical trial setting.
"The authors reported that among patients receiving the drug, when used alone or with a macrolide, they estimated a higher mortality rate".
However, WHO Director-General Tedros Adhanom Ghebreyesus said that in light of a research paper published last week in the Lancet that showed people taking hydroxychloroquine were at a higher risk of death and heart problems, there would be "a temporary pause" on the hydroxychloroquine arm of its global clinical trial.
This "Solidarity trial" is the WHO's global investigation into experimental treatments for COVID-19 - including hydroxychloroquine, as well as HIV-ARV medicine lopinavir and broad-spectrum anti-viral remdesivir, as well as interferon beta-1a.
The evidence for the efficacy of hydroxychloroquine at treating COVID-19 has always been slim at best.
"The pressure COVID-19 puts on health systems means that WHO considered the need for speed and scale in the trial", the WHO's site reads.
Worldwide studies into the effectiveness of hydroxychloroquine began after French medic Professor Didier Raoult claimed to have seen success while giving patients hydroxychloroquine and antibiotic azithromycin.
Hydroxychloroquine has been touted by US President Donald Trump and others as an effective treatment for COVID-19.
Novartis and rival Sanofi have pledged donations of tens of millions of doses of the drug, also used in rheumatoid arthritis and lupus, for COVID-19. They also implied that drugs created to stabilize cardiovascular function, including and improve endothelial cell dysfunction, including ACE inhibitors, might improve COVID-19 patient prognosis. The president has said he's been taking hydroxychloroquine to protect against the virus.
Under the new French rules, the drug can be used only in clinical trials - making it unclear if Raoult would be able to continue using it at his hospital in Marseille. The WHO has iterated that use of the drugs are generally safe for patients with malaria or autoimmune diseases.
US President Donald Trump and others have pushed hydroxychloroquine as a possible coronavirus treatment, but the World Health Organization on Monday called time in its multi-country trial, called Solidarity.
A new Lancet study has gathered thousands of cases together to present the first comprehensive observational review of hydroxychloroquine's efficacy in treating COVID-19.