Two PEP studies report no benefit of hydroxychloroquine for preventing CoV-2 infection

Simon Collins, HIV i-Base

Two studies reported lack of benefit from using hydroxychloroquine (HCQ) as PEP.

One was a randomised, double-blind, placebo-controlled trial in 821 participants reporting high-risk exposure and who started HCQ PEP within three days. Results reported no difference in COVID-19 between the two arms and were published in the NEJM. [1]

COVID-19 was confirmed in 49/414 (11.8%) vs 58/407 (14.3%) of active vs placebo arms: diff −2.4% (95% CI: −7.0 to 2.2),  p=0.35.

The second was a Spanish study that randomised more than 2300 people exposed to the CoV-2 to either HCQ or the usual care. Although not yet published, the top-line results of no difference between the two arms was reported in Science journal online. [2, 3]


  1. Boulware  DR et al. A randomized trial of hydroxychloroquine as postexposure prophylaxis for COVID-19. NEJM. DOI: 10.1056/NEJMoa2016638. (3 June 2020).
  2. Treatment of COVID-19 Cases and Chemoprophylaxis of Contacts as Prevention (HCQ4COV19).
  3. Kupferschmidt K. Three big studies dim hopes that hydroxychloroquine can treat or prevent COVID-19. Science.  (9 June 2020)

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