Abstract: JAC Research letters 8 Humeniuk R, Mathias A, Cao H et al. Safety, tolerability, and pharmacokinetics of remdesivir, an antiviral for treatment of COVID-19, in healthy subjects. Clin Transl Sci 2020; 13: 896–906. 9 FDA. Fact Sheet for Healthcare Providers Emergency Use Authorization (EUA) of VekluryV (Remdesivir). 2020. 10 Tempestilli M, Caputi P, Avataneo V et al. Pharmacokinetics of remdesivir and GS-441524 in two critically ill patients who recovered from COVID-19. J Antimicrob Chemother 2020; 75: 2977–80. R J Antimicrob Chemother 2021; 76: 827–829 doi:10.1093/jac/dkaa477 Advance Access publication 21 November 2020 Hydroxychloroquine pre-exposure prophylaxis for COVID-19 in healthcare workers ~ afiel2, Boris Revollo1, Cristian Tebe2, Judith Pen 3 1,4 Ignacio Blanco , Nuria Perez-Alvarez , Ruth Lopez5, Laura Rodriguez6, Josep Ferrer7, Pilar Ricart8, Enrique Moret9, Cristina Tural7, Anna Carreres10,  Videla1,11, Joan Matllo5, Sebastia 1,12,13 and Josep M. Llibre1* Bonaventura Clotet 1 Division of Infectious Diseases and FLS Foundation for Fighting AIDS, Infectious Diseases and Promoting Health and Science, University Hospital Germans Trias, Badalona, Spain; 2Biostatistics Unit, Bellvitge Biomedical Research Institute (IDIBELL)/University of Barcelona, L’Hospitalet de Llobregat, Barcelona, Spain; 3  de la Salut, Metropolitana Nord Laboratory, Institut Catala Badalona, Spain; 4Statistics and Operations Research Department, Universitat Politècnica de Catalunya-Barcelona Tech, Barcelona, Spain; 5Occupational Risk Prevention Unit, University Hospital Germans Trias, Badalona, Spain; 6Pulmonary Medicine, University Hospital Germans Trias, Badalona, Spain; 7 Internal Medicine Department, University Hospital Germans Trias, Badalona, Spain; 8Intensive Care Unit Division, University Hospital Germans Trias, Badalona, Spain; 9Anaesthesiology Department, University Hospital Germans Trias, Badalona, Spain; 10 Emergency Department, University Hospital Germans Trias, Badalona, Spain; 11Clinical Research Support Unit, Clinical Pharmacology Department, Bellvitge University Hospital/Bellvitge Biomedical Research Institute (IDIBELL)/University of Barcelona, *Corresponding author. E-mail: jmllibre@flsida.org Sir, Healthcare workers (HCWs) are a high-risk population for SARSCoV-2 infection and account for at least 11% of reported cases.1,2 We performed an observational cross-sectional case-control study to evaluate the efficacy of hydroxychloroquine pre-exposure prophylaxis (PrEP) among hospital HCWs. All HCWs (of all categories) who worked in the COVID-19 frontline wards of University Hospital Germans Trias (Badalona, Spain) were invited to participate. There was no protocol in the institution recommending hydroxychloroquine PrEP. The dose used by HCWs was 400 mg twice daily on the first day and 200 mg twice daily for an additional 4 days, with a maintenance dosing of 200 mg weekly thereafter. HCWs were classified as having high-risk occupational exposure if they worked in hospital-based COVID-19 wards, moderate-risk occupational exposure if they had direct contact with admitted patients, but not in COVID-19 wards, and low-risk occupational exposure if they had occasional contact with hospitalized patients. Reverse real-time PCR was performed for nasopharyngeal swabs of all HCWs with symptoms or suspicion of COVID-19. A screening of SARS-CoV-2 serology of all hospital HCWs was performed when the epidemic reached its end (late May 2020). The study..