Effectiveness of Hydroxychloroquine in COVID-19

July, 2020

Arshad et al show evidence for a reduced mortality in Covid-19 patients taking hydroxychloroquine alone or with azithromycin in an observational study in USA (Arshad et al., 2020). Data on effectiveness and toxicity of hydroxychloroquine are controversial ( Liu et al., 2020Devaux et al., 2020Gautret et al., 2020Tang et al., 2020Geleris et al., 2020).


A total of 539 COVID-19 hospitalised patients were included in our cohort in Milan, from February 24 to May 17,2020 of whom 174 died in hospital (day 14 probability of death: 29.5%–95%CI: 25.5–34.0). We divided a subset of our cohort in three groups who started treatment a median of 1 day after admission: those receiving hydroxycholoroquine alone (N = 197), those receiving hydroxycholoroquine + azithromycin (N = 94), and those receiving neither (controls) (N = 92). Of the latter group, 10 started HIV antivirals (boosted-lopinavir or –darunavir), 1 teicoplanin, 12 immunomodulatory drugs or corticosteroids, 23 heparin and 46 remained untreated. The percent of death in the 3 groups was 27%, 23% and 51%. Mechanical ventilation was used in 4.3% of hydoxychloroquine, 14.2% of hydroxycholoroquine + azithromycin and 26.1% of controls. Unweighted and weighted relative hazards of mortality are shown in Table 1. After adjusting for a number of key confounders (see table), the use of hydroxycholoroquine + azithromycin was associated with a 66% reduction in risk of death as compared to controls; the analysis also suggested a larger effectiveness of hydroxychloroquine in patients with less severe COVID-19 disease (PO2/FiO2 > 300, interaction p-value<.0001). Our results are remarkably similar to those shown by Arshad et al.

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