A careful look at hydroxychloroquine finds it ineffective in protecting exposed people from contracting COVID-19. Getty Images.
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Results to appear in Open Forum Infectious Diseases  show hydroxychloroquine does not keep people from developing COVID-19.

MEDIA CONTACT:  Susan Gregg,, 206.390.3226

People who have had close contact with people with confirmed COVID-19 infections who took hydroxychloroquine were just as likely to get COVID-19 as were those who received a placebo, according to a preliminary data analysis from a large randomized, controlled trial.  Researchers at the University of Washington Department of Global Health in Seattle led the study.

“This is a rigorous large-scale randomized, controlled clinical trial proving whether or not hydroxychloroquine is effective in preventing COVID-19, adding to less rigorously controlled studies,” said lead researcher Dr. Ruanne Barnabas, associate professor of medicine and global health at the UW School of Medicine. “The additional data we have today provides strong evidence that hydroxychloroquine offers no benefit in preventing people developing COVID-19 with a 14-day treatment course.”

The results were presented at IDWeek 2020, the Infectious Disease Society of America's annual scientific meeting,  Saturday, Oct. 24. The findings will be published in Open Forum Infectious Diseases.

Hydroxychloroquine, an antiviral medication that has been used primarily in treating malaria and for autoimmune diseases, has been touted as an effective treatment for and prophylactic against COVID-19 by a number of physicians and public figures.

Nearly 800 people participated in the trial, called the Hydroxychloroquine for COVID-19  Post-Exposure Prophylaxis, or PEP Study. All had a family member or another close contact who had tested positive for the infection. Participants were randomly assigned to take a daily tablet of hydroxychloroquine or a placebo. Both groups collected daily nasal swabs. Prevention was defined as a negative daily test for COVID-19 within 14 days of exposure to a close contact who had been infected with the pandemic coronavirus.  At the end of the study, the researchers determined that those taking the drug were just as likely to test positive as were those taking the placebo. Participants taking the drug did not report significant side effects. The rate of reported side effects was similar in both groups.

After the study reached the predetermined threshold of data required by an independent monitoring board, the researchers concluded that hydroxychloroquine was no better than the placebo.

In the United States, hydroxychloroquine is approved by the U.S. Food and Drug Administration for the treatment of malaria, discoid and systemic lupus erythematosus, and rheumatoid arthritis. It is considered safe and well-tolerated. In March, the  FDA granted Emergency Use Authorization for the use of this drug for the treatment of some COVID-19 hospitalized patients,  but rescinded the authorization in June over safety concerns and the lack of evidence of effectiveness.

See abstract at the end of this release.

The study is supported through the COVID-19 Therapeutics Accelerator, an initiative launched by the Bill & Melinda Gates Foundation, Wellcome and Mastercard, with support from an array of public and philanthropic donors, to speed up the response to the COVID-19 pandemic by identifying, assessing, developing and scaling up treatments. Its partners are committed to equitable access, including making products available and affordable in low-resource settings. The study also includes Boston Medical Center/Boston University, NYU Grossman School of Medicine, SUNY Upstate, Tulane University, University of California, Los Angeles, and University of Maryland, Baltimore.

View the  original story on UW Medicine Newsroom, and related publication in Annals of Internal Medicine.

Related media:

Gates-funded UW study shows hydroxychloroquine doesn’t prevent COVID-19, Seattle Times, Oct. 24

UW researchers find hydroxychloroquine does not prevent people from getting COVID-19, King 5, Oct. 24



Efficacy of Hydroxychloroquine for Post-exposure Prophylaxis to Prevent Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection: A Blinded, Randomized, Controlled Trial

Ruanne V. Barnabas1,2,3,7, Elizabeth R. Brown4,7,8, Anna Bershteyn9, Helen C. Stankiewicz Karita2, Christine Johnston2,5,7, Lorna E. Thorpe9, Angelica Kottkamp9, Kathleen M. Neuzil10, Miriam Laufer10, Meagan Deming10, Michael K. Paasche-Orlow11,12, Patricia J. Kissinger13, Alfred Luk14, Kristopher Paolino15, Raphael J. Landovitz16, Risa Hoffman16, Torin T. Schaafsma1, Meighan L. Krows1, Katherine K. Thomas1, Susan Morrison1, Lara Kidoguchi1, Mark Wener5,6, Alexander L. Greninger5,7, Meei-Li Huang7, Keith R. Jerome5,7, Anna Wald2,3,5,7, Connie Celum1,2,3, Helen Y. Chu1,2,3, Jared M. Baeten1,2,3, for the Hydroxychloroquine COVID-19 PEP Study Team

1Department of Global Health, 2Division of Allergy and Infectious Diseases, 3Department of Epidemiology, 4Department of Biostatistics, 5Department of Laboratory Medicine and Pathology, 6Division of Rheumatology, University of Washington, Seattle, WA; 7Vaccine and Infectious Disease Division, 8Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA; 9New York University Grossman School of Medicine, NY, NY; 10University of Maryland School of Medicine, Baltimore, MD; 11Boston University School of Medicine, 12Boston Medical Center, Boston, MA; 13School of Public Health and Tropical Medicine, 14School of Medicine, Tulane University, New Orleans, LA; 15State University of New York Upstate Medical University, Syracuse, NY; 16University of California, Los Angeles, CA


Background: Prevention interventions for coronavirus disease (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), are currently limited to non-pharmaceutical strategies. Observational and laboratory data suggested that hydroxychloroquine (HCQ) had biologic activity against SARS-CoV-2. A blinded trial of HCQ in persons with confirmed exposure and virologic and clinical endpoints is needed.

MethodsWe conducted a national, household-randomized, double-blind, controlled trial of HCQ post-exposure prophylaxis, using remote study procedures. We enrolled close contacts exposed to persons with SARS-CoV-2 infection in the past 96 hours. Participants were randomized to either HCQ (400 mg daily for three days followed by 200 mg daily for eleven days) or ascorbic acid (500 mg followed by 250 mg daily), as a placebo-equivalent control. Participants self-collected mid-turbinate swabs daily (days 1-14) for SARS-CoV-2 PCR testing. The primary outcome was PCR-confirmed, incident SARS-CoV-2 infection among persons SARS-CoV-2 negative at enrollment. Symptoms were assessed using criteria from the US CDC.

Results: From March-August 2020, 623 households were randomized; 311 households (381 participants) to the HCQ group and 312 households (400 participants) to the control group. Ninety- one percent of participants were retained up to day 14 and 9,595 of 10,588 (91%) of swabs were tested. Among participants who were SARS-CoV-2 negative at baseline (n=626/781, 80%), the cumulative incidence of  SARS-CoV-2 was 14.5% (95% CI: 11.6-17.4) and the cumulative incidence of COVID-19 symptoms was 11.6% (95% CI: 8.9-14.2) at day 14. By day 14, there was no difference between the HCQ group and control group in SARS-CoV-2 acquisition (46 vs. 43 events, aHR= 0.99, 95% CI 0.64-1.52, p=0.95) or symptomatic disease (40 vs. 32 events, aHR= 1.23, 95% CI: 0.76-1.99, p=0.40). The adverse event frequency was similar between groups (59 [15.5%] participants in the HCQ and 45 [11.3%] in the control group, p=0.092).

Conclusions: This randomized, double-blind, controlled trial among persons with recent exposure and high incidence of SAR-CoV2 provides strong evidence that HCQ post-exposure prophylaxis did not prevent SARS-CoV-2 infection or modify clinical disease.