A Randomized Trial of Hydroxychloroquine as Postexposure Prophylaxis for Covid-19

https://www.nejm.org/doi/full/10.1056/NEJMoa2016638

In this randomized, double-blind, placebo-controlled trial (NCT04308668. opens in new tab),  the efficacy of hydroxychloroquine as Covid-19 postexposure prophylaxis was investigated. In this trial, high doses of hydroxychloroquine did not prevent illness compatible with Covid-19 when initiated within 4 days after a high-risk or moderate-risk exposure. 821 asymptomatic participants were enrolled. Overall, 87.6% of the participants (719 of 821) reported a high-risk exposure to a confirmed Covid-19 contact. The incidence of new illness compatible with Covid-19 did not differ significantly between participants receiving hydroxychloroquine (49 of 414 [11.8%]) and those receiving placebo (58 of 407 [14.3%]); the absolute difference was −2.4 percentage points (95% confidence interval, −7.0 to 2.2; P=0.35). Side effects were more common with hydroxychloroquine than with placebo (40.1% vs. 16.8%), but no serious adverse reactions were reported.

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