Hydroxychloroquine as COVID-19 postexposure prophylaxis does not prevent infection
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Hydroxychloroquine did not prevent illness similar to, or confirmed to be, COVID-19 when used as postexposure prophylaxis within 4 days of moderate- to high-risk exposure, according to findings in The New England Journal of Medicine.
“The current public health strategies to mitigate [COVID-19] transmission are rapid identification of cases, isolation, contact tracing and self-quarantine of those exposed. Once a person is exposed, observation and quarantine during a 14-day incubation period is the standard of care,” David R. Boulware, MD, MPH, of the University of Minnesota, and colleagues wrote. “To date, no medication has been shown to prevent SARS-CoV-2 transmission.”
Most studies that examine chloroquine or hydroxychloroquine for COVID-19 focus on hospitalized patients, Boulware and colleagues continued, but it is not yet known whether short-term, high-dose hydroxychloroquine can prevent disease shortly after a high-risk exposure.
To explore this question, researchers conducted a randomized, double-blind, placebo-controlled trial across the United States and parts of Canada using hydroxychloroquine as postexposure prophylaxis. Boulware and colleagues enrolled 821 asymptomatic adults who had household or occupational exposure to a person with a confirmed case of COVID-19 at a distance of less than 6 feet for more than 10 minutes without a face mask or eye shield (high-risk exposure) or only using a face mask (moderate-risk exposure). Study participants were assigned to receive either placebo or hydroxychloroquine within 4 days of exposure. The regimen for hydroxychloroquine included an 800-mg dose once, followed by 600 mg in 6 to 8 hours, and then 600 mg daily for 4 more days.
Overall, the incidence of new-onset illness similar to COVID-19 did not differ between hydroxychloroquine and placebo recipients (11.8% vs. 14.3%, respectively), despite most participants (87.6%) reporting high-risk exposure to a person with confirmed COVID-19 infection. Side effects, including nausea, loose stools and abdominal discomfort, were more common with hydroxychloroquine than with placebo (40.1% vs. 16.8%, respectively; P < .001), but no serious adverse reactions were reported.
“This randomized trial did not demonstrate a significant benefit of hydroxychloroquine as postexposure prophylaxis for COVID-19,” the authors wrote. “Whether pre-exposure prophylaxis would be effective in high-risk populations is a separate question, with trials ongoing. In order to end the pandemic, a reduction in community transmission is needed.”
In an accompanying editorial, Myron S. Cohen, MD, of the Institute for Global Heath and Infectious Diseases at the University of North Carolina at Chapel Hill, said the results from Boulware and colleagues suggest the potential preventative benefit of hydroxychloroquine has yet to be determined.
“So, what are we to do with the results of this trial? The advocacy and widespread use of hydroxychloroquine seem to reflect a reasonable fear of SARS-CoV-2 infection,” Cohen wrote. “However, it would appear that, to some extent, the media and social forces — rather than medical evidence — are driving clinical decisions and the global COVID-19 research agenda.”
Cohen posed several other questions for researchers to explore moving forward. First, he asked — while acknowledging the limitations of the study by Boulware and colleagues — whether other trials of postexposure prophylaxis with hydroxychloroquine should continue if postexposure prophylaxis with hydroxychloroquine does not prevent symptomatic SARS-CoV-2 infection. Cohen also asked whether participants in other postexposure trials should be told about these results and whether the results of the current study impact trials of pre-exposure prophylaxis with hydroxychloroquine.
“The results reported by Boulware [and colleagues] are more provocative than definitive, suggesting that the potential prevention benefits of hydroxychloroquine remain to be determined,” Cohen concluded.
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