As of today, there is no antiviral for the treatment of the SARS-CoV-2 infection, and the development of a vaccine might take several months or even years. The structural superposition of the hepatitis C virus polymerase bound to sofosbuvir, a nucleoside analog antiviral approved for hepatitis C virus infections, with the SARS-CoV polymerase shows that the residues that bind to the drug are present in the latter. Moreover, a multiple alignment of several SARS-CoV-2, SARS and MERS-related coronaviruses polymerases shows that these residues are conserved in all these viruses, opening the possibility to use sofosbuvir against these highly infectious pathogens.

Background: The rst case of a corona virus 2019 (COVID-19) infection in a Sri Lankan was reported on March 11, 2020. The situation in Sri Lanka changed with the rapid increase of personnel contracting COVID-19 in a Naval base camp that housed more than 4000 people. This provided a unique opportunity to study the effectiveness of hydroxychloroquine (HCQ) for post-exposure prophylaxis (PEP), while taking stringent, non-pharmacologic, public health measures to prevent spread. Our aim is to study the effectiveness and safety of HCQ for PEP among naval personnel with exposure to COVID-19 positive patients. Methods/design: This is a placebo-controlled, randomized, clinical trial carried out in the Naval base camp and quarantine centers of the Sri Lanka Navy, Ministry of Defense, Sri Lanka. Navy personnel who are exposed to a patient with con rmed COVID-19 infection but test negative for the virus on reverse, real-time polymerase chain reaction (rRT-PCR) at recruitment will be randomized, 200 to each arm, to receive HCQ or placebo, and monitored for the development of symptoms or rRT-PCR positivity for severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) virus for 14 days. Discussion: This trial will provide high-quality evidence of the effectiveness and safety of HCQ as PEP for COVID-19. The study design is unique due to the circumstances of the outbreak in a con ned area among otherwise healthy adults, at a relatively early stage of its spread.