Correspondence Use of antiviral drugs to before potential exposure or after small sample size) in terms of clinical documented exposure to a variety of management, with published data reduce COVID-19 microbial pathogens, and in reducing expected soon. Published Online transmission the risk of secondary spread of infection. We are planning a multicentre March 19, 2020 https://doi.org/10.1016/ Based on experiences with PEP for other randomised controlled trial S2214-109X(20)30114-5 As the coronavirus disease 2019 infections, we recommend starting (NCT04304053) to evaluate the (COVID-19) spreads, efforts are being PEP as soon as possible after a recent efficacy of antiviral treatment made to reduce transmission via possible exposure to SARS-CoV-2. For in anyone found to be infected, standard public health interventions example, PEP with rifampicin is given and the efficacy of prophylactic based on isolation of cases and tracing to people exposed to index cases of hydroxychloroquine in preventing of contacts. In their modelling study, invasive meningococcal infection, and secondary SARS-CoV-2 infections Joel Hellewell and colleagues1 predict oseltamivir has been recommended by and disease symptoms among all that such a strategy could contribute to WHO for people at high risk of infection contacts. Our objective is to evaluate reducing the overall size of an outbreak, before or after exposure to pandemic the reduction in transmissibility of but will still be insufficient to achieve influenza.3 SARS-CoV-2 and in disease progression outbreak control of COVID-19 when Antiviral drugs administered shortly among the contacts of an index case. the basic reproduction number (R0) is after symptom onset can reduce The design intervention is based on higher than 1·5 or the proportion of infectiousness to others by reducing viral the design used during the Ebola ça contacts traced is lower than 80%. shedding in the respiratory secretions Suffit vaccination trial for Ebola in One of the main assumptions of the of patients (SARS-CoV-2 viral load in 2015.6 A person newly diagnosed with model by Hellewell and colleagues is sputum peaks at around 5–6 days after the disease becomes the index case, that all individuals with symptomatic symptom onset and lasts up to 14 days), around whom an epidemiologically infection with severe acute respiratory and targeted prophylactic treatment defined ring of contacts is formed. syndrome (SARS) coronavirus 2 of contacts could reduce their risk of This ring is then randomised to either (SARS-CoV-2) are eventually tested becoming infected.3 intervention or control in a 1:1 ratio on and reported. However, under the The implementation of antiviral an open-label basis. The study will be guidelines of most countries with treatment and prophylaxis has several done over the course of the COVID-19 low-grade transmission, clinicians will requirements. The stockpile of drugs outbreak in the Catalonia region of test suspected patients only if they must be adequate, the safety of Spain, with initial results expected in have travelled to an epidemic region treatment must be very high, and costs May, 2020. Identifying a treatment since the outbreak began. A second should ideally be low. The antimalarial for the prevention of COVID-19 would assumption of the model is that drug, hydroxychloroquine, is licensed change the course of the outbreak isolation of cases is 100% effective for the chemoprophylaxis and entirely. in stopping transmission. Yet home treatment of malaria and as a disease- We declare no competing interests. confinement of infected individuals modifying antirheumatic drug. It Copyright © 2020 The Author(s). Published by and contacts is challenging, efficacy has a history of being safe and well Elsevier Ltd. This is an Open Access article under the is variable, and the rigorous tracking tolerated at typical doses. Notably, the CC BY-NC-ND 4.0 license. involved requires a considerable drug shows antiviral activity in vitro *Oriol Mitjà, Bonaventura Clotet amount of public health resources. against coronaviruses, and specific­ omitja@flsida.org The current COVID-19 emergency ally, SARS-CoV-2.4 Pharmacological Infectious Diseases Department-Fight AIDS warrants the urgent development of model­ling based on observed drug Foundation, Hospital Universitari Germans Trias i potential strategies to protect people concentrations and in vitro drug Pujol, Badalona, Spain (OM, BC); and IrsiCaixa Foundation, Barcelona, Spain (BC) at high risk of infection—particularly testing suggest that prophylaxis with 1 Hellewell J, Abbott S, Gimma A, et al. Feasibility close contacts and health-care hydroxychloroquine at approved doses of controlling COVID-19 outbreaks by isolation workers, among others—even if more could prevent SARS-CoV-2 infection of cases and contacts. Lancet Glob Health 2020; robust data on antiviral therapies is and ameliorate viral shedding. 5 published online Feb 28. https://doi.org/ 10.1016/S2214-109X(20)30074-7. yet to come. A key reason for such Clinical trials of hydroxychloroquine 2 Qifang Bi, Yongsheng Wu, Shujiang Mei, et al. an approach is the high estimates for treatment for COVID-19 pneumonia Epidemiology and transmission of COVID-19 in Shenzhen China: analysis of 391 cases and the secondary attack rates of SARS- are underway in China (NCT04261517 1286 of their close contacts. medRxiv CoV-2 in households (~15%) and and NCT04307693). We are reviewing 2020;·published online March 4. among close contacts (~10%).2 Pre- the results from China as they emerge. DOI:10.1101/2020.03.03.20028423 (preprint). 3 Welliver R, Monto AS, Carewicz O, et al. exposure prophylaxis and post­exposure The first study (NCT04261517) has Effectiveness of oseltamivir in preventing prophylaxis (PEP) with antimicrobial showed positive preliminary outcomes influenza in household contacts: a randomized controlled trial. JAMA 2001; 285: 748–54. drugs are effective in preventing illness (albeit not conclusive because of the www.thelancet.com/lancetgh Vol 8 May 2020 e639 Correspondence 4 Yao X, Ye F, Zhang M, et al. In vitro antiviral activity and projection of optimized dosing design of hydroxychloroquine for the treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Clin Infect Dis 2020; published online March 9. DOI:10.1093/cid/ciaa237. 5 Tett SE, Cutler DJ, Day RO, Brown KF. Bioavailability of hydroxychloroquine tablets in healthy volunteers. Br J Clin Pharmacol 1989; 27: 771–79. 6 Henao-Restrepo AM, Camacho A, Longini IM, et al. Efficacy and effectiveness of an rVSV-vectored vaccine in preventing Ebola virus disease: final results from the Guinea ring vaccination, open-label, cluster-randomised trial (Ebola Ça Suffit!). Lancet 2017; 389: 505–18. e640 www.thelancet.com/lancetgh Vol 8 May 2020