BackgroundPre-exposure prophylaxis (PrEP) is a promising strategy to break COVID-19 transmission. Although hydroxychloroquine was evaluated for treatment and post-exposure prophylaxis, it is not evaluated for COVID-19 PrEP yet. The aim of this study was to evaluate efficacy and safety of PrEP with hydroxychloroquine against placebo in healthcare workers at high risk of SARS-CoV-2 infection during an epidemic period.MethodsWe conducted a double-blind placebo-controlled randomized clinical trial in three hospitals in Barcelona, Spain. From 350 adult healthcare workers screened, we included 269 participants with no active or past SARS-CoV-2 infection (determined by a negative nasopharyngeal SARS-CoV-2 PCR and a negative serology against SARS-CoV-2). Participants allocated in the intervention arm (PrEP) received 400mg of hydroxychloroquine daily the first four consecutive days and subsequently, 400mg weekly during the study period. Participants in the control group followed the same treatment schedule with placebo tablets. Results52.8% of participants were in the hydroxychloroquine arm and 47.2% in the placebo arm. Both groups showed similar proportion of participants experiencing at least one adverse event (AE) (p=0.548). No serious AE were reported. Almost all AE (96.4%) were mild. Only mild gastrointestinal symptoms were significantly higher in the hydroxychloroquine arm compared to the placebo arm (28.3% vs 16.9%, p=0.044). Given the national epidemic incidence decay, only one participant in each group was COVID-19 diagnosed. Consequently, our study design deemed underpowered to evaluate any benefit regarding PrEP efficacy.ConclusionsFirst month follow-up analysis displayed that PrEP with hydroxychloroquine at low doses is safe.Trial registrationThis trial was registered at clinicaltrials.gov (NCT04331834) on April 2nd 2020.

These data suggest the efficacy of dolutegravir monotherapy as a maintenance strategy to be further confirmed in randomized clinical trials.

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