Behavioral and personal characteristics associated with risk of SARS-CoV-2 infection in a Spanish university cohort.

The aim of this study is to analyze the life habits and personal factors associated with an increased SARS-CoV-2 risk in a university environment with in-person lectures during the COVID-19 pandemic. There are no previous longitudinal studies that have analyzed behavioral and personal factors with the risk of SARS-CoV-2 infection on an entire university population. A cohort study was conducted in the three campuses of the University of Navarra between August 24th 2020 and May 30th 2021, including 14,496 students and employees. 10,959 participants were finally included. Descriptive and multivariate adjusted models were performed using Cox regression. A total of 1,032 (9.4%) participants were diagnosed with COVID-19 (879 students, 153 employees), almost 50% living with their family. COVID-19 was associated with living in college or residence (HR:1.96 CI 95% 1.45 to 2.63), motor transportation (HR:1.36 CI 95% 1.14 to 1.62), South American origin (HR:1.41 CI 95% 1.17 to 1.69) and belonging to Madrid's campus (HR:3.15 CI 95% 2.50 to 3.97). In conclusion, international students, especially from Latin America, mostly lived in university apartments or shared flats and cohabited with 4-11 people. Living in a big city (Madrid), was a significant risk factor.

Photodynamic nasal SARS-CoV-2 decolonization shortens infectivity and influences specific T-Cell responses.

Background: The main objective was to evaluate the efficacy of intranasal photodynamic therapy (PDT) in SARS-CoV-2 mildly symptomatic carriers on decreasing the infectivity period. SARS-CoV-2-specific immune-stimulating effects and safety were also analysed. Methods: We performed a randomized, placebo-controlled, clinical trial in a tertiary hospital (NCT05184205). Patients with a positive SARS-CoV-2 PCR in the last 48 hours were recruited and aleatorily assigned to PDT or placebo. Patients with pneumonia were excluded. Participants and investigators were masked to group assignment. The primary outcome was the reduction in in vitro infectivity of nasopharyngeal samples at days 3 and 7. Additional outcomes included safety assessment and quantification of humoral and T-cell immune-responses. Findings: Patients were recruited between December 2021 and February 2022. Most were previously healthy adults vaccinated against COVID-19 and most carried Omicron variant. 38 patients were assigned to placebo and 37 to PDT. Intranasal PDT reduced infectivity at day 3 post-treatment when compared to placebo with a ß-coefficient of -812.2 (CI95%= -478660 - -1.3, p<0.05) infectivity arbitrary units. The probability of becoming PCR negative (ct>34) at day 7 was higher on the PDT-group, with an OR of 0.15 (CI95%=0.04-0.58). There was a decay in anti-Spike titre and specific SARS-CoV-2 T cell immunity in the placebo group 10 and 20 weeks after infection, but not in the PDT-group. No serious adverse events were reported. Interpretation: Intranasal-PDT is safe in pauci-symptomatic COVID-19 patients, it reduces SARS-CoV-2 infectivity and decelerates the decline SARS-CoV-2 specific immune-responses.

Photodynamic nasal SARS-CoV-2 decolonization shortens infectivity and influences specific T-Cell responses

Background The main objective was to evaluate the efficacy of intranasal photodynamic therapy (PDT) in SARS-CoV-2 mildly symptomatic carriers on decreasing the infectivity period. SARS-CoV-2-specific immune-stimulating effects and safety were also analysed. Methods We performed a randomized, placebo-controlled, clinical trial in a tertiary hospital (NCT05184205). Patients with a positive SARS-CoV-2 PCR in the last 48 hours were recruited and aleatorily assigned to PDT or placebo. Patients with pneumonia were excluded. Participants and investigators were masked to group assignment. The primary outcome was the reduction in in vitro infectivity of nasopharyngeal samples at days 3 and 7. Additional outcomes included safety assessment and quantification of humoral and T-cell immune-responses. Findings Patients were recruited between December 2021 and February 2022. Most were previously healthy adults vaccinated against COVID-19 and most carried Omicron variant. 38 patients were assigned to placebo and 37 to PDT. Intranasal PDT reduced infectivity at day 3 post-treatment when compared to placebo with a β-coefficient of -812.2 (CI95%= -478660 – -1.3, p<0.05) infectivity arbitrary units. The probability of becoming PCR negative (ct>34) at day 7 was higher on the PDT-group, with an OR of 0.15 (CI95%=0.04-0.58). There was a decay in anti-Spike titre and specific SARS-CoV-2 T cell immunity in the placebo group 10 and 20 weeks after infection, but not in the PDT-group. No serious adverse events were reported. Interpretation Intranasal-PDT is safe in pauci-symptomatic COVID-19 patients, it reduces SARS-CoV-2 infectivity and decelerates the decline SARS-CoV-2 specific immune-responses.

Humoral and cellular immune response over 9 months of mRNA-1273, BNT162b2 and ChAdOx1 vaccination in a University Hospital in Spain.

Scarce data have been reported about cellular immunity and longevity for different COVID-19 vaccination schedules. We carried out a prospective study enrolling 709 healthcare workers receiving two doses of mRNA-1273, BNT162b2, ChAdOx1, ChAdOx1/BNT162b2 or ChAdOx1 single dose to compare humoral and cellular immunogenicity across 9 months. Higher SARS-CoV-2 spike antibody levels were observed among individuals with hybrid immunity with one dose of any vaccine in comparison to uninfected individuals receiving two doses (mRNA-1273: 20,145 vs 4295 U/mL; BNT162b2: 15,659 vs 1959 U/mL; ChAdOx1: 5344 vs 2230 U/mL), except for ChAdOx1/BNT162b2 heterologous schedule (12,380 U/mL). Naturally infected individuals did not increase substantially the titers after the second dose and showed higher levels throughout the 9 months follow-up. The mean elimination half-life of antibodies among COVID-19 naïve participants was 98, 111, 60 and 36 days, for mRNA-1273, BNT162b2, ChAdOx1/ChAdOx1 and ChAdOx1/BNT162b2, respectively. Cellular immunity was preserved in 96%, 98%, 88% and 92% of uninfected individuals who received mRNA-1273, BNT162b2, ChAdOx1/ChAdOx1 and ChAdOx1/BNT162b2 after 6/9 months. Individuals with specific T cells showed robust long lasting protection, especially when m-RNA based vaccines are inoculated. These data may influence the validity of the vaccination passport and the need for booster vaccinations.

Neutrophil Extracellular Traps, Local IL-8 Expression, and Cytotoxic T-Lymphocyte Response in the Lungs of Patients With Fatal COVID-19.

BACKGROUND: Excessive inflammation is pathogenic in the pneumonitis associated with severe COVID-19. Neutrophils are among the most abundantly present leukocytes in the inflammatory infiltrates and may form neutrophil extracellular traps (NETs) under the local influence of cytokines. NETs constitute a defense mechanism against bacteria, but have also been shown to mediate tissue damage in a number of diseases. RESEARCH QUESTION: Could NETs and their tissue-damaging properties inherent to neutrophil-associated functions play a role in the respiratory failure seen in patients with severe COVID-19, and how does this relate to the SARS-CoV-2 viral loads, IL-8 (CXCL8) chemokine expression, and cytotoxic T-lymphocyte infiltrates? STUDY DESIGN AND METHODS: Sixteen lung biopsy samples obtained immediately after death were analyzed methodically as exploratory and validation cohorts. NETs were analyzed quantitatively by multiplexed immunofluorescence and were correlated with local levels of IL-8 messenger RNA (mRNA) and the density of CD8+ T-cell infiltration. SARS-CoV-2 presence in tissue was quantified by reverse-transcriptase polymerase chain reaction and immunohistochemistry analysis. RESULTS: NETs were found in the lung interstitium and surrounding the bronchiolar epithelium with interindividual and spatial heterogeneity. NET density did not correlate with SARS-CoV-2 tissue viral load. NETs were associated with local IL-8 mRNA levels. NETs were also detected in pulmonary thrombi and in only one of eight liver tissues. NET focal presence correlated negatively with CD8+ T-cell infiltration in the lungs. INTERPRETATION: Abundant neutrophils undergoing NETosis are found in the lungs of patients with fatal COVID-19, but no correlation was found with viral loads. The strong association between NETs and IL-8 points to this chemokine as a potentially causative factor. The function of cytotoxic T-lymphocytes in the immune responses against SARS-CoV-2 may be interfered with by the presence of NETs.

Dysautonomia in COVID-19 Patients: A Narrative Review on Clinical Course, Diagnostic and Therapeutic Strategies.

Introduction: On March 11, 2020, the World Health Organization sounded the COVID-19 pandemic alarm. While efforts in the first few months focused on reducing the mortality of infected patients, there is increasing data on the effects of long-term infection (Post-COVID-19 condition). Among the different symptoms described after acute infection, those derived from autonomic dysfunction are especially frequent and limiting. Objective: To conduct a narrative review synthesizing current evidence of the signs and symptoms of dysautonomia in patients diagnosed with COVID-19, together with a compilation of available treatment guidelines. Results: Autonomic dysfunction associated with SARS-CoV-2 infection occurs at different temporal stages. Some of the proposed pathophysiological mechanisms include direct tissue damage, immune dysregulation, hormonal disturbances, elevated cytokine levels, and persistent low-grade infection. Acute autonomic dysfunction has a direct impact on the mortality risk, given its repercussions on the respiratory, cardiovascular, and neurological systems. Iatrogenic autonomic dysfunction is a side effect caused by the drugs used and/or admission to the intensive care unit. Finally, late dysautonomia occurs in 2.5% of patients with Post-COVID-19 condition. While orthostatic hypotension and neurally-mediated syncope should be considered, postural orthostatic tachycardia syndrome (POTS) appears to be the most common autonomic phenotype among these patients. A review of diagnostic and treatment guidelines focused on each type of dysautonomic condition was done. Conclusion: Symptoms deriving from autonomic dysfunction involvement are common in those affected by COVID-19. These symptoms have a great impact on the quality of life both in the short and medium to long term. A better understanding of the pathophysiological mechanisms of Post-COVID manifestations that affect the autonomic nervous system, and targeted therapeutic management could help reduce the sequelae of COVID-19, especially if we act in the earliest phases of the disease.

Therapeutic versus Prophylactic Bemiparin in Hospitalized Patients with Nonsevere COVID-19 Pneumonia (BEMICOP Study): An Open-Label, Multicenter, Randomized, Controlled Trial.

Thromboprophylaxis with low molecular weight heparin in hospitalized patients with COVID-19 is mandatory, unless contraindicated. Given the links between inflammation and thrombosis, the use of higher doses of anticoagulants could improve outcomes. We conducted an open-label, multicenter, randomized, controlled trial in adult patients hospitalized with nonsevere COVID-19 pneumonia and elevated D-dimer. Patients were randomized to therapeutic-dose bemiparin (115 IU/kg daily) versus standard prophylaxis (bemiparin 3,500 IU daily), for 10 days. The primary efficacy outcome was a composite of death, intensive care unit admission, need of mechanical ventilation support, development of moderate/severe acute respiratory distress, and venous or arterial thrombosis within 10 days of enrollment. The primary safety outcome was major bleeding (International Society on Thrombosis and Haemostasis criteria). A prespecified interim analysis was performed when 40% of the planned study population was reached. From October 2020 to May 2021, 70 patients were randomized at 5 sites and 65 were included in the primary analysis; 32 patients allocated to therapeutic dose and 33 to standard prophylactic dose. The primary efficacy outcome occurred in 7 patients (22%) in the therapeutic-dose group and 6 patients (18%) in the prophylactic-dose (absolute risk difference 3.6% [95% confidence interval [CI], -16% -24%]; odds ratio 1.26 [95% CI, 0.37-4.26]; p = 0.95). Discharge in the first 10 days was possible in 66 and 79% of patients, respectively. No major bleeding event was registered. Therefore, in patients with COVID-19 hospitalized with nonsevere pneumonia but elevated D-dimer, the use of a short course of therapeutic-dose bemiparin does not appear to improve clinical outcomes compared with standard prophylactic doses. Trial Registration: ClinicalTrials.gov NCT04604327.

Persistence of High Levels of Serum Complement C5a in Severe COVID-19 Cases After Hospital Discharge.

Evidence supports a role of complement anaphylatoxin C5a in the pathophysiology of COVID-19. However, information about the evolution and impact of C5a levels after hospital discharge is lacking. We analyzed the association between circulating C5a levels and the clinical evolution of hospitalized patients infected with SARS-CoV-2. Serum C5a levels were determined in 32 hospitalized and 17 non-hospitalized patients from Clinica Universidad de Navarra. One hundred and eighty eight serial samples were collected during the hospitalization stay and up to three months during the follow-up. Median C5a levels were 27.71 ng/ml (25th to 75th percentile: 19.35-34.96) for samples collected during hospitalization, versus 16.76 ng/ml (12.90-25.08) for samples collected during the follow-up (p<0.001). There was a negative correlation between serum C5a levels and the number of days from symptom onset (p<0.001). C5a levels also correlated with a previously validated clinical risk score (p<0.001), and was associated with the severity of the disease (p<0.001). An overall reduction of C5a levels was observed after hospital discharge. However, elevated C5a levels persisted in those patients with high COVID-19 severity (i.e. those with a longest stay in the hospital), even after months from hospital discharge (p=0.020). Moreover, high C5a levels appeared to be associated with the presence of long-term respiratory symptoms (p=0.004). In conclusion, serum C5a levels remain high in severe cases of COVID-19, and are associated with the presence of respiratory symptoms after hospital discharge. These results may suggest a role for C5a in the long-term effects of COVID-19 infection.

Preclinical evaluation of a synthetic peptide vaccine against SARS-CoV-2 inducing multiepitopic and cross-reactive humoral neutralizing and cellular CD4 and CD8 responses.

Identification of relevant epitopes is crucial for the development of subunit peptide vaccines inducing neutralizing and cellular immunity against SARS-CoV-2. Our aim was the characterization of epitopes in the receptor-binding domain (RBD) of SARS-CoV-2 spike (S) protein to generate a peptide vaccine. Epitope mapping using a panel of 10 amino acid overlapped 15-mer peptides covering region 401-515 from RBD did not identify linear epitopes when tested with sera from infected individuals or from RBD-immunized mice. However, immunization of mice with these 15-mer peptides identified four peptides located at region 446-480 that induced antibodies recognizing the peptides and RBD/S1 proteins. Immunization with peptide 446-480 from S protein formulated with Freund's adjuvant or with CpG oligodeoxinucleotide/Alum induced polyepitopic antibody responses in BALB/c and C56BL/6J mice, recognizing RBD (titres of 3 × 104-3 × 105, depending on the adjuvant) and displaying neutralizing capacity (80-95% inhibition capacity; p < 0.05) against SARS-CoV-2. Murine CD4 and CD8T-cell epitopes were identified in region 446-480 and vaccination experiments using HLA transgenic mice suggested the presence of multiple human T-cell epitopes. Antibodies induced by peptide 446-480 showed broad recognition of S proteins and S-derived peptides belonging to SARS-CoV-2 variants of concern. Importantly, vaccination with peptide 446-480 or with a cyclic version of peptide 446-488 containing a disulphide bridge between cysteines 480 and 488, protected humanized K18-hACE2 mice from a lethal dose of SARS-CoV-2 (62.5 and 75% of protection; p < 0.01 and p < 0.001, respectively). This region could be the basis for a peptide vaccine or other vaccine platforms against Covid-19.

Immunological Biomarkers of Fatal COVID-19: A Study of 868 Patients.

Information on the immunopathobiology of coronavirus disease 2019 (COVID-19) is rapidly increasing; however, there remains a need to identify immune features predictive of fatal outcome. This large-scale study characterized immune responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection using multidimensional flow cytometry, with the aim of identifying high-risk immune biomarkers. Holistic and unbiased analyses of 17 immune cell-types were conducted on 1,075 peripheral blood samples obtained from 868 COVID-19 patients and on samples from 24 patients presenting with non-SARS-CoV-2 infections and 36 healthy donors. Immune profiles of COVID-19 patients were significantly different from those of age-matched healthy donors but generally similar to those of patients with non-SARS-CoV-2 infections. Unsupervised clustering analysis revealed three immunotypes during SARS-CoV-2 infection; immunotype 1 (14% of patients) was characterized by significantly lower percentages of all immune cell-types except neutrophils and circulating plasma cells, and was significantly associated with severe disease. Reduced B-cell percentage was most strongly associated with risk of death. On multivariate analysis incorporating age and comorbidities, B-cell and non-classical monocyte percentages were independent prognostic factors for survival in training (n=513) and validation (n=355) cohorts. Therefore, reduced percentages of B-cells and non-classical monocytes are high-risk immune biomarkers for risk-stratification of COVID-19 patients.

Immunogenicity and crossreactivity of antibodies to the nucleocapsid protein of SARS-CoV-2: utility and limitations in seroprevalence and immunity studies.

COVID-19 patients elicit strong responses to the nucleocapsid (N) protein of SARS-CoV-2 but binding antibodies are also detected in prepandemic individuals, indicating potential crossreactivity with common cold human coronaviruses (HCoV) and questioning its utility in seroprevalence studies. We investigated the immunogenicity of the full-length and shorter fragments of the SARS-CoV-2 N protein, and the crossreactivity of antibodies with HCoV. We identified a C-terminus region in SARS-CoV2 N of minimal sequence homology with HCoV that was more specific for SARS-CoV-2 and highly immunogenic. IgGs to the full-length SARS-CoV-2 N also recognized N229E N, and IgGs to HKU1 N recognized SARS-CoV-2 N. Crossreactivity with SARS-CoV-2 was stronger for alpha- rather than beta-HCoV despite having less sequence identity, revealing the importance of conformational recognition. Higher preexisting IgG to OC43 N correlated with lower IgG to SARS-CoV-2 N in rRT-PCR negative individuals, reflecting less exposure and indicating a potential protective association. Antibodies to SARS-CoV-2 N were higher in patients with more severe and longer duration of symptoms and in females. IgGs remained stable for at least 3 months, while IgAs and IgMs declined faster. In conclusion, N protein is a primary target of SARS-CoV-2-specific and HCoV crossreactive antibodies, both of which may affect the acquisition of immunity to COVID-19.

Highly Sensitive and Specific Multiplex Antibody Assays To Quantify Immunoglobulins M, A, and G against SARS-CoV-2 Antigens.

Reliable serological tests are required to determine the prevalence of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to characterize immunity to the disease in order to address key knowledge gaps in the coronavirus disease 2019 (COVID-19) pandemic. Quantitative suspension array technology (qSAT) assays based on the xMAP Luminex platform overcome the limitations of rapid diagnostic tests and enzyme-linked immunosorbent assays (ELISAs) with their higher precision, dynamic range, throughput, miniaturization, cost-efficiency, and multiplexing capacity. We developed three qSAT assays for IgM, IgA, and IgG against a panel of eight SARS-CoV-2 antigens, including spike protein (S), nucleocapsid protein (N), and membrane protein (M) constructs. The assays were optimized to minimize the processing time and maximize the signal-to-noise ratio. We evaluated their performances using 128 prepandemic plasma samples (negative controls) and 104 plasma samples from individuals with SARS-CoV-2 diagnosis (positive controls), of whom 5 were asymptomatic, 51 had mild symptoms, and 48 were hospitalized. Preexisting IgG antibodies recognizing N, M, and S proteins were detected in negative controls, which is suggestive of cross-reactivity to common-cold coronaviruses. The best-performing antibody/antigen signatures had specificities of 100% and sensitivities of 95.78% at ≥14 days and 95.65% at ≥21 days since the onset of symptoms, with areas under the curve (AUCs) of 0.977 and 0.999, respectively. Combining multiple markers as assessed by qSAT assays has the highest efficiency, breadth, and versatility to accurately detect low-level antibody responses for obtaining reliable data on the prevalence of exposure to novel pathogens in a population. Our assays will allow gaining insights into antibody correlates of immunity and their kinetics, required for vaccine development to combat the COVID-19 pandemic.

The effect of early treatment with ivermectin on viral load, symptoms and humoral response in patients with non-severe COVID-19: A pilot, double-blind, placebo-controlled, randomized clinical trial.

BACKGROUND: Ivermectin inhibits the replication of SARS-CoV-2 in vitro at concentrations not readily achievable with currently approved doses. There is limited evidence to support its clinical use in COVID-19 patients. We conducted a Pilot, randomized, double-blind, placebo-controlled trial to evaluate the efficacy of a single dose of ivermectin reduce the transmission of SARS-CoV-2 when administered early after disease onset. METHODS: Consecutive patients with non-severe COVID-19 and no risk factors for complicated disease attending the emergency room of the Clínica Universidad de Navarra between July 31, 2020 and September 11, 2020 were enrolled. All enrollments occurred within 72 h of onset of fever or cough. Patients were randomized 1:1 to receive ivermectin, 400 mcg/kg, single dose (n = 12) or placebo (n = 12). The primary outcome measure was the proportion of patients with detectable SARS-CoV-2 RNA by PCR from nasopharyngeal swab at day 7 post-treatment. The primary outcome was supported by determination of the viral load and infectivity of each sample. The differences between ivermectin and placebo were calculated using Fisher's exact test and presented as a relative risk ratio. This study is registered at ClinicalTrials.gov: NCT04390022. FINDINGS: All patients recruited completed the trial (median age, 26 [IQR 19-36 in the ivermectin and 21-44 in the controls] years; 12 [50%] women; 100% had symptoms at recruitment, 70% reported headache, 62% reported fever, 50% reported general malaise and 25% reported cough). At day 7, there was no difference in the proportion of PCR positive patients (RR 0·92, 95% CI: 0·77-1·09, p = 1·0). The ivermectin group had non-statistically significant lower viral loads at day 4 (p = 0·24 for gene E; p = 0·18 for gene N) and day 7 (p = 0·16 for gene E; p = 0·18 for gene N) post treatment as well as lower IgG titers at day 21 post treatment (p = 0·24). Patients in the ivermectin group recovered earlier from hyposmia/anosmia (76 vs 158 patient-days; p < 0.001). INTERPRETATION: Among patients with non-severe COVID-19 and no risk factors for severe disease receiving a single 400 mcg/kg dose of ivermectin within 72 h of fever or cough onset there was no difference in the proportion of PCR positives. There was however a marked reduction of self-reported anosmia/hyposmia, a reduction of cough and a tendency to lower viral loads and lower IgG titers which warrants assessment in larger trials. FUNDING: ISGlobal, Barcelona Institute for Global Health and Clínica Universidad de Navarra.

Histopathological findings in fatal COVID-19 severe acute respiratory syndrome: preliminary experience from a series of 10 Spanish patients.

In December 2019, an outbreak of severe acute respiratory syndrome associated to SARS-CoV2 was reported in Wuhan, China. To date, little is known on histopathological findings in patients infected with the new SARS-CoV2. Lung histopathology shows features of acute and organising diffuse alveolar damage. Subtle cellular inflammatory infiltrate has been found in line with the cytokine storm theory. Medium-size vessel thrombi were frequent, but capillary thrombi were not present. Despite the elevation of biochemical markers of cardiac injury, little histopathological damage could be confirmed. Viral RNA from paraffin sections was detected at least in one organ in 90% patients.

The SARS-CoV-2 Ivermectin Navarra-ISGlobal Trial (SAINT) to Evaluate the Potential of Ivermectin to Reduce COVID-19 Transmission in low risk, non-severe COVID-19 patients in the first 48 hours after symptoms onset: A structured summary of a study protocol for a randomized control pilot trial.

OBJECTIVES: The primary objective is to determine the efficacy of a single dose of ivermectin, administered to low risk, non-severe COVID-19 patients in the first 48 hours after symptom onset to reduce the proportion of patients with detectable SARS-CoV-2 RNA by Polymerase Chain Reaction (PCR) test from nasopharyngeal swab at day 7 post-treatment. The secondary objectives are: 1.To assess the efficacy of ivermectin to reduce the SARS-CoV-2 viral load in the nasopharyngeal swab at day 7 post treatment.2.To assess the efficacy of ivermectin to improve symptom progression in treated patients.3.To assess the proportion of seroconversions in treated patients at day 21.4.To assess the safety of ivermectin at the proposed dose.5.To determine the magnitude of immune response against SARS-CoV-2.6.To assess the early kinetics of immunity against SARS-CoV-2. TRIAL DESIGN: SAINT is a single centre, double-blind, randomized, placebo-controlled, superiority trial with two parallel arms. Participants will be randomized to receive a single dose of 400 µg/kg ivermectin or placebo, and the number of patients in the treatment and placebo groups will be the same (1:1 ratio). PARTICIPANTS: The population for the study will be patients with a positive nasopharyngeal swab PCR test for SARS-CoV-2, with non-severe COVID-19 disease, and no risk factors for progression to severity. Vulnerable populations such as pregnant women, minors (i.e.; under 18 years old), and seniors (i.e.; over 60 years old) will be excluded. Inclusion criteria 1. Patients diagnosed with COVID-19 in the emergency room of the Clínica Universidad de Navarra (CUN) with a positive SARS-CoV-2 PCR. 2. Residents of the Pamplona basin ("Cuenca de Pamplona"). 3. The patient must be between the ages of 18 and 60 years of age. 4. Negative pregnancy test for women of child bearing age*. 5. The patient or his/her representative, has given informed consent to participate in the study. 6. The patient should, in the PI's opinion, be able to comply with all the requirements of the clinical trial (including home follow up during isolation). Exclusion criteria 1. Known history of ivermectin allergy. 2. Hypersensitivity to any component of ivermectin. 3. COVID-19 pneumonia. Diagnosed by the attending physician.Identified in a chest X-ray. 4. Fever or cough present for more than 48 hours. 5. Positive IgG against SARS-CoV-2 by rapid diagnostic test. 6. Age under 18 or over 60 years. 7. The following co-morbidities (or any other disease that might interfere with the study in the eyes of the PI): Immunosuppression.Chronic Obstructive Pulmonary Disease.Diabetes.Hypertension.Obesity.Acute or chronic renal failure.History of coronary disease.History of cerebrovascular disease.Current neoplasm. 8. Recent travel history to countries that are endemic for Loa loa (Angola, Cameroon, Central African Republic, Chad, Democratic Republic of Congo, Ethiopia, Equatorial, Guinea, Gabon, Republic of Congo, Nigeria and Sudan). 9. Current use of CYP 3A4 or P-gp inhibitor drugs such as quinidine, amiodarone, diltiazem, spironolactone, verapamil, clarithromycin, erythromycin, itraconazole, ketoconazole, cyclosporine, tacrolimus, indinavir, ritonavir or cobicistat. Use of critical CYP3A4 substrate drugs such as warfarin. *Women of child bearing age may participate if they use a safe contraceptive method for the entire period of the study and at least one month afterwards. A woman is considered to not have childbearing capacity if she is post-menopausal (minimum of 2 years without menstruation) or has undergone surgical sterilization (at least one month before the study). The trial is currently planned at a single center, Clínica Universidad de Navarra, in Navarra (Spain), and the immunology samples will be analyzed at the Barcelona Institute for Global Health (ISGlobal), in Barcelona (Spain). Participants will be recruited by the investigators at the emergency room and/or COVID-19 area of the CUN. They will remain in the trial for a period of 28 days at their homes since they will be patients with mild disease. In the interest of public health and to contain transmission of infection, follow-up visits will be conducted in the participant's home by a clinical trial team comprising nursing and medical members. Home visits will assess clinical and laboratory parameters of the patients. INTERVENTION AND COMPARATOR: Ivermectin will be administered to the treatment group at a 400µg/Kg dose (included in the EU approved label of Stromectol and Scabioral). The control group will receive placebo. There is no current data on the efficacy of ivermectin against the virus in vivo, therefore the use of placebo in the control group is ethically justified. MAIN OUTCOMES: Primary Proportion of patients with a positive SARS-CoV-2 PCR from a nasopharyngeal swab at day 7 post-treatment. Secondary 1.Mean viral load as determined by PCR cycle threshold (Ct) at baseline and on days 4, 7, 14, and 21.2.Proportion of patients with fever and cough at days 4, 7, 14, and 21 as well as proportion of patients progressing to severe disease or death during the trial.3.Proportion of patients with seroconversion at day 21.4.Proportion of drug-related adverse events during the trial.5.Median levels of IgG, IgM, IgA measured by Luminex, frequencies of innate and SARS-CoV-2-specific T cells assessed by flow cytometry, median levels of inflammatory and activation markers measured by Luminex and transcriptomics.6.Median kinetics of IgG, IgM, IgA levels during the trial, until day 28. RANDOMISATION: Eligible patients will be allocated in a 1:1 ratio using a randomization list generated by the trial statistician using blocks of four to ensure balance between the groups. A study identification code with the format "SAINT-##" (##: from 01 to 24) will be generated using a sequence of random numbers so that the randomization number does not match the subject identifier. The sequence and code used will be kept in an encrypted file accessible only to the trial statistician. A physical copy will be kept in a locked cabinet at the CUN, accessible only to the person administering the drug who will not enrol or attend to patient care. A separate set of 24 envelopes for emergency unblinding will be kept in the study file. BLINDING (MASKING): The clinical trial team and the patients will be blinded. The placebo will not be visibly identical, but it will be administered by staff not involved in the clinical care or participant follow up. NUMBERS TO BE RANDOMISED (SAMPLE SIZE): The sample size is 24 patients: 12 participants will be randomised to the treatment group and 12 participants to the control group. TRIAL STATUS: Current protocol version: 1.0 dated 16 of April 2020. Recruitment is envisioned to begin by May 14th and end by June 14th. TRIAL REGISTRATION: EudraCT number: 2020-001474-29, registered April 1st. Clinicaltrials.gov: submitted, pending number 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.