Abstract: RESEARCH Matthieu Mahévas,1 Viet-Thi Tran,2 Mathilde Roumier,3 Amélie Chabrol,4 Romain Paule,3 Constance Guillaud,1 Elena Fois,1 Raphael Lepeule,5 Tali-Anne Szwebel,6 François-Xavier Lescure,7 Frédéric Schlemmer,8 Marie Matignon,9 Mehdi Khellaf,1 Etienne Crickx,1 Benjamin Terrier,6 Caroline Morbieu,6 Paul Legendre,6 Julien Dang,2 Yoland Schoindre,3 Jean-Michel Pawlotsky,10 Marc Michel,1 Elodie Perrodeau,2 Nicolas ­Carlier,11 Nicolas Roche,11 Victoire de Lastours,12 Clément Ourghanlian,13 Solen Kerneis,14 Philippe Ménager,15 Luc Mouthon,6 Etienne Audureau,16 Philippe Ravaud,2 Bertrand Godeau,1 Sébastien Gallien,17 Nathalie Costedoat-Chalumeau2,6 For numbered affiliations see end of the article Correspondence to: M Mahévas matthieu.mahevas@gmail.com (ORCID 0000-0001-9182-1434) Additional material is published online only. To view please visit the journal online. Cite this as: BMJ 2020;369:m1844 http://dx.doi.org/10.1136/bmj.m1844 Accepted: 5 May 2020 ABSTRACT OBJECTIVE To assess the effectiveness of hydroxychloroquine in patients admitted to hospital with coronavirus disease 2019 (covid-19) pneumonia who require oxygen. DESIGN Comparative observational study using data collected from routine care. SETTING Four French tertiary care centres providing care to patients with covid-19 pneumonia between 12 March and 31 March 2020. PARTICIPANTS 181 patients aged 18-80 years with documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia who required oxygen but not intensive care. INTERVENTIONS Hydroxychloroquine at a dose of 600 mg/day within 48 hours of admission to hospital (treatment group) versus standard care without hydroxychloroquine (control group). MAIN OUTCOME MEASURES The primary outcome was survival without transfer to the intensive care unit at day 21. Secondary WHAT IS ALREADY KNOWN ON THIS TOPIC Treatments are urgently needed to prevent respiratory failure and deaths from coronavirus disease 2019 (covid-19) An in vitro study has reported potential activity by hydroxychloroquine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for covid-19 Small studies of hydroxychloroquine treatment in patients with covid-19 have reported promising results WHAT THIS STUDY ADDS In patients admitted to hospital with covid-19 pneumonia who require oxygen, hydroxychloroquine seemed to have no effect on reducing admissions to intensive care or deaths at day 21 after hospital admission Hydroxychloroquine treatment did not have any effect on survival without acute respiratory distress syndrome at day 21 after hospital admission The results of this study do not support the use of hydroxychloroquine in these patients the bmj | BMJ 2020;369:m1844 | doi: 10.1136/bmj.m1844 outcomes were overall survival, survival without acute respiratory distress syndrome, weaning from oxygen, and discharge from hospital to home or rehabilitation (all at day 21). Analyses were adjusted for confounding factors by inverse probability of treatment weighting. RESULTS In the main analysis, 84 patients who received hydroxychloroquine within 48 hours of admission to hospital (treatment group) were compared with 89 patients who did not receive hydroxychloroquine (control group). Eight additional patients received hydroxychloroquine more than 48 hours after admission. In the weighted analyses, the survival rate without transfer to the intensive care unit at day 21 was 76% in the treatment group and 75% in the control group..