Epidemiological and Genomic Analysis of a Large SARS-CoV-2 Outbreak in a Long-Term Care Facility in Catalonia, Spain.

Limiting outbreaks in long-term care facilities (LTCFs) is a cornerstone strategy to avoid an excess of COVID-19-related morbidity and mortality and to reduce its burden on the health system. We studied a large outbreak that occurred at an LTCF, combining methods of classical and genomic epidemiology analysis. The outbreak lasted for 31 days among residents, with an attack rate of 98% and 57% among residents and staff, respectively. The case fatality rate among residents was 16% (n = 15). Phylogenetic analysis of 59 SARS-CoV-2 isolates revealed the presence of two closely related viral variants in all cases (B.1.177 lineage), revealing a far more complex outbreak than initially thought and suggesting an initial spread driven by staff members. In turn, our results suggest that resident relocations to mitigate viral spread might have increased the risk of infection for staff members, creating secondary chains of transmission that were responsible for prolonging the outbreak. Our results highlight the importance of considering unnoticed chains of transmission early during an outbreak and making an adequate use and interpretation of diagnostic tests. Outbreak containment measures should be carefully tailored to each LTCF. IMPORTANCE The impact of COVID-19 on long-term care facilities (LTCFs) has been disproportionately large due to the high frailty of the residents. Here, we report epidemiological and genomic findings of a large outbreak that occurred at an LTCF, which ultimately affected almost all residents and nearly half of staff members. We found that the outbreak was initially driven by staff members; however, later resident relocation to limit the outbreak resulted in transmission from residents to staff members, evidencing the complexity and different phases of the outbreak. The phylogenetic analysis of SARS-CoV-2 isolates indicated that two closely related variants were responsible for the large outbreak. Our study highlights the importance of combining methods of classical and genomic epidemiology to take appropriate outbreak containment measures in LTCFs.

Progression to lung fibrosis in severe COVID-19 patients: A morphological and transcriptomic study in postmortem samples.

The development of lung fibrosis is a major concern in patients recovered from severe COVID-19 pneumonia. This study aimed to document the evolution of diffuse alveolar damage (DAD) to the fibrosing pattern and define the transcriptional programs involved. Morphological, immunohistochemical and transcriptional analysis were performed in lung samples obtained from autopsy of 33 severe COVID-19 patients (median illness duration: 36 days). Normal lung and idiopathic pulmonary fibrosis (IPF) were used for comparison. Twenty-seven patients with DAD and disease evolution of more than 2 weeks had fibrosis. Pathways and genes related with collagen biosynthesis and extracellular matrix (ECM) biosynthesis and degradation, myofibroblastic differentiation and epithelial to mesenchymal transition (EMT) were overexpressed in COVID-19. This pattern had similarities with that observed in IPF. By immunohistochemistry, pathological fibroblasts (pFBs), with CTHRC1 and SPARC expression, increased in areas of proliferative DAD and decreased in areas of mature fibrosis. Immunohistochemical analysis demonstrated constitutive expression of cadherin-11 in normal epithelial cells and a similar pattern of cadherin and catenin expression in epithelial cells from both normal and COVID-19 samples. Transcriptomic analysis revealed downregulation of the Hippo pathway, concordant with the observation of YAP overexpression in hyperplastic alveolar epithelial cells. Progression to fibrosis in severe COVID-19 is associated with overexpression of fibrogenic pathways and increased in CTHRC1- and SPARC-positive pFBs. Whereas the Hippo pathway seemed to be implicated in the response to epithelial cell damage, EMT was not a major process implicated in COVID-19 mediated lung fibrosis.

Melatonin in the Prophylaxis of SARS-CoV-2 Infection in Healthcare Workers (MeCOVID): A Randomised Clinical Trial.

We evaluated in this randomised, double-blind clinical trial the efficacy of melatonin as a prophylactic treatment for prevention of SARS-CoV-2 infection among healthcare workers at high risk of SARS-CoV-2 exposure. Healthcare workers fulfilling inclusion criteria were recruited in five hospitals in Spain and were randomised 1:1 to receive melatonin 2 mg administered orally for 12 weeks or placebo. The main outcome was the number of SARS-CoV-2 infections. A total of 344 volunteers were screened, and 314 were randomised: 151 to placebo and 163 to melatonin; 308 received the study treatment (148 placebo; 160 melatonin). We detected 13 SARS-CoV-2 infections, 2.6% in the placebo arm and 5.5% in the melatonin arm (p = 0.200). A total of 294 adverse events were detected in 127 participants (139 in placebo; 155 in melatonin). We found a statistically significant difference in the incidence of adverse events related to treatment: 43 in the placebo arm and 67 in the melatonin arm (p = 0.040), and in the number of participants suffering from somnolence related to treatment: 8.8% (n = 14) in the melatonin versus 1.4% (n = 2) in the placebo arm (p = 0.008). No severe adverse events related to treatment were reported. We cannot confirm our hypothesis that administration of melatonin prevents the development of SARS-CoV-2 infection in healthcare workers.

Health Care Workers' Reasons for Choosing Between Two Different COVID-19 Prophylaxis Trials in an Acute Pandemic Context: Single-Center Questionnaire Study.

BACKGROUND: In April 2020, two independent clinical trials to assess SARS-CoV-2 prophylaxis strategies among health care workers were initiated at our hospital: MeCOVID (melatonin vs placebo) and EPICOS (tenofovir disoproxil/emtricitabine vs hydroxychloroquine vs combination therapy vs placebo). OBJECTIVE: This study aimed to evaluate the reasons why health care workers chose to participate in the MeCOVID and EPICOS trials, as well as why they chose one over the other. METHODS: Both trials were offered to health care workers through an internal news bulletin. After an initial screening visit, all subjects were asked to respond to a web-based survey. RESULTS: In the first month, 206 health care workers were screened and 160 were randomized. The survey participation was high at 73.3%. Health care workers cited "to contribute to scientific knowledge" (n=80, 53.0%), followed by "to avoid SARS-CoV-2 infection" (n=33, 21.9%) and "the interest to be tested for SARS-CoV-2" (n=28, 18.5%), as their primary reasons to participate in the trials. We observed significant differences in the expected personal benefits across physicians and nurses (P=.01). The vast majority of volunteers (n=202, 98.0%) selected the MeCOVID trial, their primary reason being their concern regarding adverse reactions to treatments in the EPICOS trial (n=102, 69.4%). CONCLUSIONS: Health care workers' reasons to participate in prophylaxis trials in an acute pandemic context appear to be driven largely by their desire to contribute to science and to gain health benefits. Safety outweighed efficacy when choosing between the two clinical trials.

Age-Adjusted Endothelial Activation and Stress Index for Coronavirus Disease 2019 at Admission Is a Reliable Predictor for 28-Day Mortality in Hospitalized Patients With Coronavirus Disease 2019.

Background: Endothelial Activation and Stress Index (EASIX) predict death in patients undergoing allogeneic hematopoietic stem cell transplantation who develop endothelial complications. Because coronavirus disease 2019 (COVID-19) patients also have coagulopathy and endotheliitis, we aimed to assess whether EASIX predicts death within 28 days in hospitalized COVID-19 patients. Methods: We performed a retrospective study on COVID-19 patients from two different cohorts [derivation (n = 1,200 patients) and validation (n = 1,830 patients)]. The endpoint was death within 28 days. The main factors were EASIX [(lactate dehydrogenase * creatinine)/thrombocytes] and aEASIX-COVID (EASIX * age), which were log2-transformed for analysis. Results: Log2-EASIX and log2-aEASIX-COVID were independently associated with an increased risk of death in both cohorts (p < 0.001). Log2-aEASIX-COVID showed a good predictive performance for 28-day mortality both in the derivation cohort (area under the receiver-operating characteristic = 0.827) and in the validation cohort (area under the receiver-operating characteristic = 0.820), with better predictive performance than log2-EASIX (p < 0.001). For log2 aEASIX-COVID, patients with low/moderate risk (<6) had a 28-day mortality probability of 5.3% [95% confidence interval (95% CI) = 4-6.5%], high (6-7) of 17.2% (95% CI = 14.7-19.6%), and very high (>7) of 47.6% (95% CI = 44.2-50.9%). The cutoff of log2 aEASIX-COVID = 6 showed a positive predictive value of 31.7% and negative predictive value of 94.7%, and log2 aEASIX-COVID = 7 showed a positive predictive value of 47.6% and negative predictive value of 89.8%. Conclusion: Both EASIX and aEASIX-COVID were associated with death within 28 days in hospitalized COVID-19 patients. However, aEASIX-COVID had significantly better predictive performance than EASIX, particularly for discarding death. Thus, aEASIX-COVID could be a reliable predictor of death that could help to manage COVID-19 patients.

Harmonized D-dimer levels upon admission for prognosis of COVID-19 severity: Results from a Spanish multicenter registry (BIOCOVID-Spain study).

Coagulopathy is a key feature of COVID-19 and D-dimer has been reported as a predictor of severity. However, because D-dimer test results vary considerably among assays, resolving harmonization issues is fundamental to translate findings into clinical practice. In this retrospective multicenter study (BIOCOVID study), we aimed to analyze the value of harmonized D-dimer levels upon admission for the prediction of in-hospital mortality in COVID-19 patients. All-cause in-hospital mortality was defined as endpoint. For harmonization of D-dimer levels, we designed a model based on the transformation of method-specific regression lines to a reference regression line. The ability of D-dimer for prediction of death was explored by receiver operating characteristic curves analysis and the association with the endpoint by Cox regression analysis. Study population included 2663 patients. In-hospital mortality rate was 14.3%. Harmonized D-dimer upon admission yielded an area under the curve of 0.66, with an optimal cut-off value of 0.945 mg/L FEU. Patients with harmonized D-dimer ≥ 0.945 mg/L FEU had a higher mortality rate (22.4% vs. 9.2%; p < 0.001). D-dimer was an independent predictor of in-hospital mortality, with an adjusted hazard ratio of 1.709. This is the first study in which a harmonization approach was performed to assure comparability of D-dimer levels measured by different assays. Elevated D-dimer levels upon admission were associated with a greater risk of in-hospital mortality among COVID-19 patients, but had limited performance as prognostic test.

The COVID-19 Scenario in Terms of Gender: A Preliminary Analysis in IBEX-35 Companies

The COVID-19 pandemic has had serious consequences on employment and recent reports have warned that the impacts of the crisis are never gender-neutral. The objective of this research is to analyse the variations that have existed in terms of female representation in the Spanish listed companies during the COVID-19 scenario. The integrated annual reports and the non-financial information reports of each company have been examined to identify the changes that have occurred in their governance structures, leadership positions, and total workforce. A descriptive and correlational analysis was carried out in 2019 and 2020. The findings reveal that: (1) there has been a slight increase in the figures of female representation in different hierarchical positions;(2) the proportion of women on the boards of directors does not depend on the number of women in lower positions;and (3) there is a positive relationship between female representation in leadership positions and the number of women in the total workforce. These results have important implications for business sustainability in the medium and long term.

Cardiac troponin and COVID-19 severity: Results from BIOCOVID study.

BACKGROUND: Myocardial injury is a common finding in COVID-19 strongly associated with severity. We analysed the prevalence and prognostic utility of myocardial injury, characterized by elevated cardiac troponin, in a large population of COVID-19 patients, and further evaluated separately the role of troponin T and I. METHODS: This is a multicentre, retrospective observational study enrolling patients with laboratory-confirmed COVID-19 who were hospitalized in 32 Spanish hospitals. Elevated troponin levels were defined as values above the sex-specific 99th percentile upper reference limit, as recommended by international guidelines. Thirty-day mortality was defined as endpoint. RESULTS: A total of 1280 COVID-19 patients were included in this study, of whom 187 (14.6%) died during the hospitalization. Using a nonspecific sex cut-off, elevated troponin levels were found in 344 patients (26.9%), increasing to 384 (30.0%) when a sex-specific cut-off was used. This prevalence was significantly higher (42.9% vs 21.9%; P < .001) in patients in whom troponin T was measured in comparison with troponin I. Sex-specific elevated troponin levels were significantly associated with 30-day mortality, with adjusted odds ratios (ORs) of 3.00 for total population, 3.20 for cardiac troponin T and 3.69 for cardiac troponin I. CONCLUSION: In this multicentre study, myocardial injury was a common finding in COVID-19 patients. Its prevalence increased when a sex-specific cut-off and cardiac troponin T were used. Elevated troponin was an independent predictor of 30-day mortality, irrespective of cardiac troponin assay and cut-offs to detect myocardial injury. Hence, the early measurement of cardiac troponin may be useful for risk stratification in COVID-19.

Characteristics and laboratory findings on admission to the emergency department among 2873 hospitalized patients with COVID-19: the impact of adjusted laboratory tests in multicenter studies. A multicenter study in Spain (BIOCOVID-Spain study).

Identification of predictors for severe disease progression is key for risk stratification in COVID-19 patients. We aimed to describe the main characteristics and identify the early predictors for severe outcomes among hospitalized patients with COVID-19 in Spain. This was an observational, retrospective cohort study (BIOCOVID-Spain study) including COVID-19 patients admitted to 32 Spanish hospitals. Demographics, comorbidities and laboratory tests were collected. Outcome was in-hospital mortality. For analysis, laboratory tests values were previously adjusted to assure the comparability of results among participants. Cox regression was performed to identify predictors. Study population included 2873 hospitalized COVID-19 patients. Nine variables were independent predictors for in-hospital mortality, including creatinine (Hazard ratio [HR]:1.327; 95% Confidence Interval [CI]: 1.040-1.695, p = .023), troponin (HR: 2.150; 95% CI: 1.155-4.001; p = .016), platelet count (HR: 0.994; 95% CI: 0.989-0.998; p = .004) and C-reactive protein (HR: 1.037; 95% CI: 1.006-1.068; p = .019). This is the first multicenter study in which an effort was carried out to adjust the results of laboratory tests measured with different methodologies to guarantee their comparability. We reported a comprehensive information about characteristics in a large cohort of hospitalized COVID-19 patients, focusing on the analytical features. Our findings may help to identify patients early at a higher risk for an adverse outcome.

La otorrinolaringología y el riesgo de contraer el nuevo coronavirus humano COVID-19

La pandemia de enfermedad por coronavirus 2019 (COVID- 19) ha producido cambios sin precedentes en la comunidad médica. Los médicos y trabajadores de la salud que realizan o participan en exámenes o procedimientos de cabeza y cuello y de la vía aérea son susceptibles en alto riesgo de adquirir la infección por COVID 19 debido a la alta exposición a aerosoles y contaminación por gotas. En la actualidad se carece de datos de riesgo específico de infección. Sin embargo, los otorrinolaringólogos y cirujanos de cabeza y cuello, junto con los oftalmólogos y los odontólogos, son los grupos de mayor riesgo dentro de los profesionales de la salud debido a las áreas que examinan. Este documento se desarrolla con base en pautas encontradas en la literatura disponible más reciente. Es seguro que serán modificadas según la experiencia de cada país. La enfermedad por Coronavirus 2019 (COVID-19) es causada por un nuevo coronavirus (SARS-Cov-2). Los síntomas más comunes son fiebre y tos seca, aunque la mayoría de los pacientes reportan otros síntomas como cefalea, odinofagia y estornudos. La enfermedad se originó en Wuhan, China, y rápidamente se diseminó en todo el país asiático y a otros países (1). Por desgracia, como es conocido, ya llegó a Colombia. A la fecha (27/03/2020), han sido diagnosticados 920 239 casos en el mundo, con 46 153 muertes globales (OMS). En Colombia hay 1065 casos y 17 muertes (Instituto Nacional de Salud-INS). La secuencia específica del SARS-Cov-2 ha sido encontrada en secreciones pulmonares y en hisopados de orofaringe y nasofaringe de pacientes enfermos (1). Por esta razón, los médicos que están en contacto cercano con la cara de los pacientes, como los otorrinolaringólogos, oftalmólogos y odontólogos están en mayor riesgo de infectarse

Transfusion support in COVID-19 patients: Impact on hospital blood component supply during the outbreak.

BACKGROUND: During the COVID-19 outbreak, most hospitals deferred elective surgical procedures to allow space for the overwhelming number of COVID-19 patient admissions, expecting a decrease in routine blood component requirements. However, because transfusion support needs of COVID-19 patients are not well known, its impact on hospital blood supply is uncertain. The objective of this study was to assess the effect of the COVID-19 pandemic on transfusion demand. STUDY DESIGN AND METHODS: Transfusion records during the peak of the COVID-19 pandemic (March 1-April 30, 2020) were reviewed in our center to assess changes in blood requirements. RESULTS: During this period 636 patients received a total of 2934 blood components, which reflects a 17.6% reduction in transfusion requirements with regard to the same period of 2019, and blood donations in Madrid dropped by 45%. The surgical blood demand decreased significantly during the outbreak (50.2%). Blood usage in the hematology and oncology departments remained unchanged, while the day ward demand halved, and intensive care unit transfusion needs increased by 116%. A total of 6.2% of all COVID inpatients required transfusion support. COVID-19 inpatients consumed 19% of all blood components, which counterbalanced the savings owed to the reduction in elective procedures. CONCLUSION: Although only a minority of COVID-19 inpatients required transfusion, the expected reduction in transfusion needs caused by the lack of elective surgical procedures is partially offset by the large number of admitted patients during the peak of the pandemic. This fact must be taken into account when planning hospital blood supply.

Telemedicina en la práctica del otorrinolaringólogo en el período de contingencia del COVID-19

Introducción: la pandemia por el nuevo coronavirus nos ha afectado a todos y muchos hemos tenido que cerrar o disminuir sustancialmente nuestra práctica. Sin embargo, es necesario mantener la comunicación con nuestros pacientes que continúan requiriendo de nuestra atención y manejo. Es aquí donde la telemedicina en otorrinolaringología desempeña un papel muy importante. Métodos: se realizó una revisión narrativa de la literatura mediante una búsqueda en PUB-MED y EMBASE a conveniencia con respecto a la información disponible sobre telesalud y telemedicina en el área de la otorrinolaringología. Además, se incluyó literatura de asociaciones de otorrinolaringología a nivel mundial y lineamientos y normas del gobierno colombiano. Discusión: la telemedicina es una herramienta útil para la atención de pacientes durante esta contingencia. Debemos seguir ciertos parámetros, elegir adecuadamente a los pacientes y actuar con honestidad y buena fe. Se realizan sugerencias del beneficio de la telesalud y telemedicina, consideraciones especiales en nuestra práctica médica, alcances de los servicios mencionados e implementación de estos en nuestros consultorios e instituciones basados en la literatura disponible, normas legales y experiencia de los autores. Conclusión: en la práctica del otorrinolaringólogo, es posible implementar la telemedicina con el aval de las aseguradoras y la aceptación de los pacientes. Se debe ser extremadamente cuidadoso con el diligenciamiento de la historia clínica, con la formulación de medicamentos y la selección adecuada de los pacientes. La telemedicina en otorrinolaringología es una herramienta valiosa, que nos permite continuar atendiendo a pacientes seleccionados, al tiempo que los cuidamos a ellos y a nosotros. Introduction: The pandemic due to the novel Coronavirus has affected all of us affecting substantially our practice. However, it is necessary to maintain communication with our patients who continue to require our services. It is here where telehealth and telemedicine in Otolaryngology play an important role. Methods: A narrative review of the literature was carried out through a search in PUB-MED and EMBASE regarding the information available on telehealth and telemedicine in the area of Otolaryngology. In addition, literature from Otolaryngology societies worldwide and guidelines and regulations of the Colombian government were included. Discussion: Telemedicine is useful for patient care in this contingency. We must follow certain parameters, carefully choose patients, and act in good faith. Suggestions are made on the benefit of telehealth and telemedicine, special considerations in our medical practice, the scope of the aforementioned services and their implementation in our offices and institutions based on the available literature, legal regulations and the authors'experience. Conclusion: In the practice of the Otolaryngologist it is possible to implement telemedicine with the endorsement of the insurers and the acceptance of patients. One must be extremely careful with the medical record and the prescription of medications and select patients appropriately. Otolaryngology telemedicine is a valuable tool that allows us to continue caring for selected patients by keeping them and ourselves safe.

La otorrinolaringología y el riesgo de contraer el nuevo coronavirus humano COVID-19

La pandemia de enfermedad por coronavirus 2019 (COVID-19) ha producido cambios sin precedentes en la comunidad médica. Los médicos y trabajadores de la salud que realizan o participan en exámenes o procedimientos de cabeza y cuello y de la vía aérea son susceptibles en alto riesgo de adquirir la infección por COVID 19 debido a la alta exposición a aerosoles y contaminación por gotas. En la actualidad se carece de datos de riesgo específico de infección. Sin embargo, los otorrinolaringólogos y cirujanos de cabeza y cuello, junto con los oftalmólogos y los odontólogos, son los grupos de mayor riesgo dentro de los profesionales de la salud debido a las áreas que examinan. Este documento se desarrolla con base en pautas encontradas en la literatura disponible más reciente. Es seguro que serán modificadas según la experiencia de cada país. The 2019 coronavirus disease (COVID-19) pandemic has produced unprecedented changes in the medical community. Physicians and healthcare workers who perform or participate in head and neck and airway examinations and procedures are at high risk of acquiring COVID 19 infection due to high exposure to aerosols and drop contamination. Currently there is not specific infection risk data available. However, otolaryngologists and head and neck surgeons, along with ophthalmologists and dentists, are the highest risk groups within healthcare professionals due to the areas they examine. This document is developed based on guidelines found in the most recent available literature that will most likely be modified according to the experience on the pandemic of each country.

Risk factors and outcome of COVID-19 in patients with hematological malignancies.

BACKGROUND: Prognostic factors of poor outcome in patients with hematological malignancies and COVID-19 are poorly defined. PATIENTS AND METHODS: This was a Spanish transplant group and cell therapy (GETH) multicenter retrospective observational study, which included a large cohort of blood cancer patients with laboratory-confirmed SARS-CoV-2 infection through PCR assays from March 1st 2020 to May 15th 2020. RESULTS: We included 367 pediatric and adult patients with hematological malignancies, including recipients of autologous (ASCT) (n = 58) or allogeneic stem cell transplantation (allo-SCT) (n = 65) from 41 hospitals in Spain. Median age of patients was 64 years (range 1-93.8). Recipients of ASCT and allo-SCT showed lower mortality rates (17% and 18%, respectively) compared to non-SCT patients (31%) (p = 0.02). Prognostic factors identified for day 45 overall mortality (OM) by logistic regression multivariate analysis included age > 70 years [odds ratio (OR) 2.1, 95% confidence interval (CI) 1.2-3.8, p = 0.011]; uncontrolled hematological malignancy (OR 2.9, 95% CI 1.6-5.2, p < 0.0001); ECOG 3-4 (OR, 2.56, 95% CI 1.4-4.7, p = 0.003); neutropenia (< 0.5 × 109/L) (OR 2.8, 95% CI 1.3-6.1, p = 0.01); and a C-reactive protein (CRP) > 20 mg/dL (OR 3.3, 95% CI 1.7-6.4, p < 0.0001). In multivariate analysis of 216 patients with very severe COVID-19, treatment with azithromycin or low dose corticosteroids was associated with lower OM (OR 0.42, 95% CI 0.2-0.89 and OR 0.31, 95% CI 0.11-0.87, respectively, p = 0.02) whereas the use of hidroxycloroquine did not show significant improvement in OM (OR 0.64, 95% CI 0.37-1.1, P = 0.1). CONCLUSIONS: In most patients with hematological malignancies COVID-19 mortality was directly driven by older age, disease status, performance status, as well as by immune (neutropenia) parameters and level of inflammation (high CRP). Use of azithromycin and low dose corticosteroids may be of value in very severe COVID-19.

A randomized multicenter clinical trial to evaluate the efficacy of melatonin in the prophylaxis of SARS-CoV-2 infection in high-risk contacts (MeCOVID Trial): A structured summary of a study protocol for a randomised controlled trial.

OBJECTIVES: Primary objective: to evaluate the efficacy of melatonin as a prophylactic treatment on prevention of symptomatic SARS-CoV-2 infection among healthcare workers at high risk of SARS-CoV-2 exposure. Secondary objectives: To evaluate the efficacy of melatonin as a prophylactic treatment on prevention of asymptomatic SARS-CoV-2 infection.To evaluate the efficacy of melatonin to prevent the development of severe COVID-19 in the participants enrolled in this study who develop SARS-CoV-2 infection along the trial.To evaluate the duration of COVID-19 symptoms in participants receiving melatonin before the infection.To evaluate seroconversion timing post-symptom onset. Exploratory objectives:To compare severity of COVID-19 between men and women.To evaluate the influence of sleep and diet on prevention from SARS-CoV-2 infection.To evaluate the effect of melatonin on the incidence and characteristics of lymphopenia and increase of inflammatory cytokines related to COVID-19. TRIAL DESIGN: This is a two-arm parallel randomised double-blind controlled trial to evaluate the efficacy of melatonin versus placebo in the prophylaxis of coronavirus disease 2019 among healthcare workers. PARTICIPANTS: Inclusion Criteria: Male or female participants ≥ 18 and ≤ 80 years of age.Healthcare workers from the public and private Spanish hospital network at risk of SARS-CoV 2 infection.Not having a previous COVID19 diagnosis.Understanding the purpose of the trial and not having taken any pre-exposure prophylaxis (PrEP) including HIV PrEP from March 1st 2020 until study enrolment.Having a negative SARS-CoV 2 reverse-transcription PCR (RT-PCR) result or a negative serologic rapid test (IgM/IgG) result before randomization.Premenopausal women must have a negative urinary pregnancy test in the 7 days before starting the trial treatment.Premenopausal women and males with premenopausal couples must commit to using a high efficiency anticonceptive method. EXCLUSION CRITERIA: HIV infection.Active hepatitis B infection.Renal failure (CrCl < 60 mL/min/1.73 m2) or need for hemodialysis.Osteoporosis.Myasthenia gravis.Pre-existent maculopathy.Retinitis pigmentosa.Bradycardia (less than 50 bpm).Weight less than 40 Kg.Participant with any immunosuppressive condition or hematological disease.Treatment with drugs that may prolong QT in the last month before randomization for more than 7 days including: azithromycin, chlorpromazine, cisapride, clarithromycin, domperidone, droperidol, erythromycin, halofantrine, haloperidol, lumefantrine, mefloquine, methadone, pentamidine, procainamide, quinidine, quinine, sotalol, sparfloxacin, thioridazine, amiodarone.Hereditary intolerance to galactose, Lapp lactase deficiency or glucose or galactose malabsorption.Treatment with fluvoxamine.Treatment with benzodiazepines or benzodiazepine analogues such as zolpidem, zopiclone or zaleplon.Pregnancy.Breastfeeding.History of potentially immune derived diseases such as: lupus, Crohn's disease, ulcerative colitis, vasculitis or rheumatoid arthritis.Insulin-dependent diabetes mellitus.Known history of hypersensitivity to the study drug or any of its components.Patients that should not be included in the study at the judgment of the research team. Participants will be recruited from the following eight hospitals in Madrid, Spain: Hospital Universitario La Paz, Hospital Ramón y Cajal, Hospital Infanta Sofía, Hospital 12 de Octubre, Hospital Clínico San Carlos, Hospital Central de la defensa Gómez Ulla,Hospital de La Princesa and Hospital Infanta Leonor. INTERVENTION AND COMPARATOR: Experimental: Melatonin (Circadin®, Exeltis Healthcare, Spain): 2 mg of melatonin orally before bedtime for 12 weeks. Comparator: Identical looking placebo (Laboratorios Liconsa, Spain) orally before bedtime for 12 weeks. MAIN OUTCOMES: Number of SARS-CoV-2 (COVID-19) symptomatic infections confirmed by polymerase chain reaction (PCR) test or serologic test or according to each centre diagnosis protocol. Primary outcome will be measured until the end of treatment for each participant (until the date of the last dose taken by each patient). RANDOMISATION: Patients who meet all inclusion and no exclusion criteria will be randomised, stratified by centres, sex and age (<50 and ≥ 50 years old). The randomisation sequence was created using SAS version 9.4 statistical software (procedure 'PROC PLAN') with a 1:1 allocation. No randomisation seed was specified. The randomisation seed was generated taking the hour of the computer where the program was executed. Randomization will be done centrally through the electronic system RedCAP® in order to conceal the sequence until interventions are assigned BLINDING (MASKING): Participants, caregivers, and those assessing the outcomes are blinded to group assignment. NUMBERS TO BE RANDOMISED (SAMPLE SIZE): A total of 450 participants are planned to be enrolled in this clinical trial, 225 in the experimental arm and 225 in the placebo arm. TRIAL STATUS: Protocol version 3.0, 17th of April 2020. Recruitment ongoing. First participant was recruited on the 21st of April 2020. The final participant is anticipated to be recruited on the 31st of May 2020. As of May 18th, 2020, a total of 312 participants have been enrolled (154 at Hospital La Paz, 85 at Hospital Infanta Sofía and 73 at Hospital 12 de Octubre). TRIAL REGISTRATION: EU Clinical Trials Register: 2020-001530-35; Date of trial registration: 13th of April 2020; https://www.clinicaltrialsregister.eu/ctr-search/trial/2020-001530-35/ES FULL PROTOCOL: The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest in expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.