800 mg once, followed by 600 mg in 6 to 8 h, then 600 mgdaily for 4 additional daysPlacebo group  The incidence of new illness compatible with Covid-19 did not differ significantly between the HCQ group (49 of 414 (11.8%)) and the placebo group (58 of 407 (14.3%)); the absolute difference was −2.4 percentage points (95% confidence interval, −7.0 to 2.2; p = 0.35).