Borba et al [49]. Randomized controlled trial High-dose CQ group: n = 40;Low-dose CQ group:n = 41 high-dose CQ (600 mg/2 times/day, for 10 day);low-dose CQ (450 mg/2 times/day for 5 days, double dose on 1st day) The mortality rate in the high-dose group was more than double that in low-dose group Double-blind study; 2 dosages of CQ for the first time in severe COVID-19 Small sample size; single-center design; Lack of a placebo control; Lack of exclusion criteria based on the QTc interval at baseline