A malaria drug taken by US President Donald Trump to prevent Covid-19 did not show any benefit versus placebo in reducing coronavirus infection among healthcare workers, according to clinical trial results published on Wednesday, Reuters reports.

The study largely confirms results from a clinical trial in June that showed hydroxychloroquine was ineffective in preventing infection among people exposed to the new coronavirus.

Trump began backing hydroxychloroquine early in the pandemic and told reporters in May he started taking the drug after two White House staffers tested positive for Covid-19. Studies have found the drug to offer little benefit as a treatment.