The two primary outcomes analyzed in the study were death and the need for ventilation.

About 28 percent who were given hydroxychloroquine plus usual care died, versus 11 percent of those getting routine care alone.

About 22 percent of those getting the drug plus azithromycin died too, but the difference between that group and usual care was not considered large enough to rule out other factors that could have affected survival.

Hydroxychloroquine made no difference in the need for a breathing machine, either.

The researchers said, “In this study, we found no evidence that use of hydroxychloroquine, either with or without azithromycin, reduced the risk of mechanical ventilation in patients hospitalized with Covid-19. An association of increased overall mortality was identified in patients treated with hydroxychloroquine alone. These findings highlight the importance of awaiting the results of ongoing prospective, randomized, controlled studies before widespread adoption of these drugs.”

Researchers did not track side effects but noted hints that hydroxychloroquine might have damaged other organs. The drug has long been known to have potentially serious side effects, including altering the heartbeat in a way that could lead to sudden death.