Hydroxychloroquine for prophylaxis of COVID-19 in health workers: A randomized clinical trial

PLoS One. 2022 Feb 9;17(2):e0261980. doi: 10.1371/journal.pone.0261980. eCollection 2022.


Introduction: Health care workers are at high risk of being infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our aim is to evaluate the efficacy and safety of hydroxychloroquine (HCQ) for prophylaxis of coronavirus disease 19 (COVID-19) in health personnel exposed to patients infected by SARS-CoV-2.

Methods: Double-blind randomized, placebo-controlled single center clinical trial. Included subjects were health care workers caring for severe COVID-19 patients. Main outcome was time to symptomatic SARS-CoV-2 infection.

Results: 127 subjects with a confirmed baseline negative RT-PCR SARS-CoV2 test were included in the trial. 62 assigned to HCQ and 65 to placebo. One subject (1.6%) in the HCQ group and 6 (9.2%) subjects in the placebo group developed COVID-19 (Log-Rank test p = 0.07). No severe COVID-19 cases were observed. The study was suspended because of a refusal to participate and losses to follow up after several trials reported lack of effectiveness of hydroxychloroquine in hospitalized patients with COVID-19.

Conclusion: The effect size of hydroxychloroquine was higher than placebo for COVID-19 symptomatic infection in health personnel, although this was not statistically significant. The trial is underpowered due to the failure to complete the estimated sample size.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antimalarials / therapeutic use*
  • Antiviral Agents / therapeutic use*
  • COVID-19 / diagnosis
  • COVID-19 / prevention & control*
  • Double-Blind Method
  • Female
  • Health Personnel
  • Humans
  • Hydroxychloroquine / therapeutic use*
  • Male
  • Placebo Effect
  • SARS-CoV-2 / drug effects
  • SARS-CoV-2 / isolation & purification
  • Treatment Outcome


  • Antimalarials
  • Antiviral Agents
  • Hydroxychloroquine

Grants and funding

Support for the trial was received from the Instituto Nacional de Enfermedades Respiratorias (National Institute of Respiratory Diseases, https://www.gob.mx/salud/iner), from CONACYT (National Council of Science and Technology https://www.conacyt.gob.mx/), via a grant to RPP, and by SANOFI (https://www.sanofi.com.mx/) through a investigator-sponsored trial including the tested drug and identical placebo. SANOFI gave some financial support for the study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.