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New England Journal of Medicine: Hydroxychloroquine Ineffective to Prevent COVID-19


Coronavirus studies by Engin Akyurt via

A study published in the New England Journal of Medicine (NEJM) on June 3 reports that prophylactive (preventitive) treatment with hydroxychloroquine (HCQ) does not work.  The study was randomized, double-blinded (neither treating physician nor patient knew which treatment was used) and placebo-controlled (active drug and placebo were given to separate groups.)  This represents the “gold standard” for this type of treatment, which is why the paper was accepted for publication by the NEJM– which is the “gold standard” journal for medical studies.

There is little to say, other than to quote the article itself:

We enrolled adults who had household or occupational exposure to someone with confirmed Covid-19 at a distance of less than 6 ft for more than 10 minutes while wearing neither a face mask nor an eye shield (high-risk exposure) or while wearing a face mask but no eye shield (moderate-risk exposure). Within 4 days after exposure, we randomly assigned participants to receive either placebo or hydroxychloroquine (800 mg once, followed by 600 mg in 6 to 8 hours, then 600 mg daily for 4 additional days). The primary outcome was the incidence of either laboratory-confirmed Covid-19 or illness compatible with Covid-19 within 14 days.


We enrolled 821 asymptomatic participants. 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.


After high-risk or moderate-risk exposure to Covid-19, hydroxychloroquine did not prevent illness compatible with Covid-19 or confirmed infection when used as postexposure prophylaxis within 4 days after exposure.

The study was definitely large enough, and the results definitely showed no significant difference between groups.  The rest of the paper is a disquisition on the virus itself and the way the study was done.  We can conclude that 1) there is no evidence that HCQ is beneficial at preventing COVID-19 when given after exposure and 2) He-who-must-not-be-named will either ignore this study or call it “fake news.”

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