Hydroxychloroquine as postexposure prophylaxis to prevent severe acute respiratory syndrome coronavirus 2 infection a randomized trial

Ruanne V. Barnabas, Elizabeth R. Brown, Anna Bershteyn, Helen C.Stankiewicz Karita, Christine Johnston, Lorna E. Thorpe, Angelica Kottkamp, Kathleen M. Neuzil, Miriam K. Laufer, Meagan Deming, Michael K. Paasche-Orlow, Patricia J. Kissinger, Alfred Luk, Kristopher Paolino, Raphael J. Landovitz, Risa Hoffman, Torin T. Schaafsma, Meighan L. Krows, Katherine K. Thomas, Susan MorrisonHarald S. Haugen, Lara Kidoguchi, Mark Wener, Alexander L. Greninger, Meei Li Huang, Keith R. Jerome, Anna Wald, Connie Celum, Helen Y. Chu, Jared M. Baeten

Research output: Contribution to journalArticlepeer-review


BACKGROUND: Effective prevention against coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently limited to nonpharmaceutical strategies. Laboratory and observational data suggested that hydroxychloroquine had biological activity against SARS-CoV-2, potentially permitting its use for prevention.

OBJECTIVE: To test hydroxychloroquine as postexposure prophylaxis for SARS-CoV-2 infection.

DESIGN: Household-randomized, double-blind, controlled trial of hydroxychloroquine postexposure prophylaxis. (ClinicalTrials.gov: NCT04328961).

SETTING: National U.S. multicenter study.

PARTICIPANTS: Close contacts recently exposed (<96 hours) to persons with diagnosed SARS-CoV-2 infection.

INTERVENTION: Hydroxychloroquine (400 mg/d for 3 days followed by 200 mg/d for 11 days) or ascorbic acid (500 mg/d followed by 250 mg/d) as a placebo-equivalent control.

MEASUREMENTS: Participants self-collected mid-turbinate swabs daily (days 1 to 14) for SARS-CoV-2 polymerase chain reaction (PCR) testing. The primary outcome was PCR-confirmed incident SARS-CoV-2 infection among persons who were SARS-CoV-2 negative at enrollment.

RESULTS: Between March and August 2020, 671 households were randomly assigned: 337 (407 participants) to the hydroxychloroquine group and 334 (422 participants) to the control group. Retention at day 14 was 91%, and 10 724 of 11 606 (92%) expected swabs were tested. Among the 689 (89%) participants who were SARS-CoV-2 negative at baseline, there was no difference between the hydroxychloroquine and control groups in SARS-CoV-2 acquisition by day 14 (53 versus 45 events; adjusted hazard ratio, 1.10 [95% CI, 0.73 to 1.66]; P  > 0.20). The frequency of participants experiencing adverse events was higher in the hydroxychloroquine group than the control group (66 [16.2%] versus 46 [10.9%], respectively; P  = 0.026).

LIMITATION: The delay between exposure, and then baseline testing and the first dose of hydroxychloroquine or ascorbic acid, was a median of 2 days.

CONCLUSION: This rigorous randomized controlled trial among persons with recent exposure excluded a clinically meaningful effect of hydroxychloroquine as postexposure prophylaxis to prevent SARS-CoV-2 infection.

PRIMARY FUNDING SOURCE: Bill & Melinda Gates Foundation.

Original languageEnglish (US)
Pages (from-to)344-352
Number of pages9
JournalAnnals of internal medicine
Issue number3
StatePublished - Mar 1 2021


  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Antiviral Agents/adverse effects
  • COVID-19/diagnosis
  • COVID-19 Nucleic Acid Testing
  • Double-Blind Method
  • Female
  • Humans
  • Hydroxychloroquine/adverse effects
  • Male
  • Middle Aged
  • Post-Exposure Prophylaxis
  • SARS-CoV-2
  • Time Factors
  • Treatment Outcome
  • United States
  • Young Adult

ASJC Scopus subject areas

  • Internal Medicine


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