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In March 2020, the World Health Organization (WHO) declared coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 1 , a pandemic. With rapidly accumulating numbers of cases and deaths reported globally 2 , a vaccine is urgently needed. Here we report the available safety, tolerability and immunogenicity data from an ongoing placebo-controlled, observer-blinded dose-escalation study (ClinicalTrials.gov identifier NCT04368728) among 45 healthy adults (18–55 years of age), who were randomized to receive 2 doses—separated by 21 days—of 10 μg, 30 μg or 100 μg of BNT162b1. BNT162b1 is a lipid-nanoparticle-formulated, nucleoside-modified mRNA vaccine that encodes the trimerized receptor-binding domain (RBD) of the spike glycoprotein of SARS-CoV-2. Local reactions and systemic events were dose-dependent, generally mild to moderate, and transient. A second vaccination with 100 μg was not administered because of the increased reactogenicity and a lack of meaningfully increased immunogenicity after a single dose compared with the 30-μg dose. RBD-binding IgG concentrations and SARS-CoV-2 neutralizing titres in sera increased with dose level and after a second dose. Geometric mean neutralizing titres reached 1.9–4.6-fold that of a panel of COVID-19 convalescent human sera, which were obtained at least 14 days after a positive SARS-CoV-2 PCR. These results support further evaluation of this mRNA vaccine candidate. In a dose-escalation study of the COVID-19 RNA vaccine BNT162b1 in 45 healthy adults, RBD-binding IgG concentrations and SARS-CoV-2 neutralizing titres in sera increased with dose level and after a second vaccine dose.

Objectives To evaluate the efficacy of two doses of the adsorbed vaccine COVID-19 (inactivated) produced by Sinovac in symptomatic individuals, with virological confirmation of COVID-19, two weeks after the completion of the two-dose vaccination regimen, aged 18 years or older who work as health professionals providing care to patients with possible or confirmed COVID-19. To describe the occurrence of adverse reactions associated with the administration of each of two doses of the adsorbed vaccine COVID-19 (inactivated) produced by Sinovac up to one week after vaccination in Adults (18-59 years of age) and Elderly (60 years of age or more). Trial design This is a Phase III, randomized, multicenter, endpoint driven, double-blind, placebo-controlled clinical trial to assess the efficacy and safety of the adsorbed vaccine COVID-19 (inactivated) produced by Sinovac. The adsorbed vaccine COVID-19 (inactivated) produced by Sinovac (product under investigation) will be compared to placebo. Voluntary participants will be randomized to receive two intramuscular doses of the investigational product or the placebo, in a 1: 1 ratio, stratified by age group (18 to 59 years and 60 years or more) and will be monitored for one year by active surveillance of COVID-19. Two databases will be established according to the age groups: one for adults (18-59 years) and one for the elderly (60 years of age or older). The threshold to consider the vaccine efficacious will be to reach a protection level of at least 50%, as proposed by the World Health Organization and the FDA. Success in this criterion will be defined by sequential monitoring with adjustment of the lower limit of the 95% confidence interval above 30% for the primary efficacy endpoint. Participants Healthy participants and / or participants with clinically controlled disease, of both genders, 18 years of age or older, working as health professionals performing care in units specialized in direct contact with people with possible or confirmed cases of COVID-19. Participation of pregnant women and those who are breastfeeding, as well as those intending to become pregnant within three months after vaccination will not be allowed. Participants will only be included after signing the voluntary Informed Consent Form and ensuring they undergo screening evaluation and conform to all the inclusion and exclusion criteria. All the clinical sites are located in Brazil. Intervention and comparator Experimental intervention: The vaccine was manufactured by Sinovac Life Sciences (Beijing, China) and contains 3 μg/0.5 mL (equivalent to 600 SU per dose) of inactivated SARS-CoV-2 virus, and aluminium hydroxide as adjuvant. Control comparator: The placebo contains aluminium hydroxide in a 0.5 mL solution The schedule of both, experimental intervention and placebo is two 0.5 mL doses IM (deltoid) with a two week interval. Main outcomes The primary efficacy endpoint is the incidence of symptomatic cases of virologically confirmed COVID-19 two weeks after the second vaccination. The virological diagnosis will be confirmed by detection of SARS-CoV-2 nucleic acid in a clinical sample. The primary safety endpoint is the frequency of solicited and unsolicited local and systemic adverse reactions during the period of one week after vaccination according to age group in adult (18-59 years old) and elder (60 years of age or older) subjects. Adverse reactions are defined as adverse events that have a reasonable causal relationship to vaccination. Randomisation There will be two randomization lists, one for each age group, based on the investigational products to be administered, i.e ., vaccine or placebo at a 1: 1 ratio. Each randomization list will be made to include up to 11,800 (18-59 year-old) adults, and 1,260 elderly (60 y-o and older) participants, the maximum number of participants needed per age group. An electronic central randomization system will be used to designate the investigational product that each participant must receive. Blinding (masking) This trial is designed as a double-blind study to avoid introducing bias in the evaluation of efficacy, safety and immunogenicity. The clinical care team, the professionals responsible for the vaccination and the participants will not know which investigational product will be administered. Only pharmacists or nurses in the study who are responsible for the randomization, separation and blinding of the investigational product will have access to unblinded information. The sponsor's operational team will also remain blind. Numbers to be randomised (sample size) The total number of participants needed to evaluate efficacy, 13,060 participants, satisfies the needed sample size calculated to evaluate safety. Therefore, the total number obtained for efficacy will be the number retained for the study. Up to 13,060 participants are expected to enter the study, with up to 11,800 participants aged 18 to 59 years and 1,260 elderly participants aged 60 and over. Half of the participants of each group will receive the experimental vaccine and half of them will receive the placebo. The recruitment of participants may be modified as recommended by the Data Safety Monitoring Committee at time of the interim unblinded analysis or blind assessment of the COVID-19 attack rate during the study. Trial Status Protocol version 2.0 – 24-Aug-2020. Recruitment started on July 21 st , 2020. The recruitment is expected to conclude in October 2020. Trial registration ClinicalTrials.gov Identifier: NCT0445659 . Registry on 2 July 2020 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.

At present, there are no proven agents for treatment of coronavirus disease (COVID-19). The available evidence has not allowed guidelines to clearly recommend any drugs outside the context of clinical trials. The novel coronavirus SARS-CoV-2 that causes COVID-19 invokes a hyperinflammatory state driven by multiple cells and mediators like interleukin (IL)-1, IL-6, IL-12, and IL-18, tumor necrosis factor alpha (TNFα), etc. Considering the proven role of cytokine dysregulation in causing this hyperinflammation in the lungs with IL-6 being a key driver, particularly in seriously ill COVID-19 patients, it is crucial to further explore selective cytokine blockade with drugs like the IL-6 inhibitors tocilizumab, sarilumab, and siltuximab. These targeted monoclonal antibodies can dampen the downstream IL-6 signaling pathways, which can lead to decreased cell proliferation, differentiation, oxidative stress, exudation, and improve clinical outcomes in patients with evident features of cytokine-driven inflammation like persistent fever, dyspnea and elevated markers. Preliminary evidence has come for tocilizumab from some small studies, and interim analysis of a randomized controlled trial; the latter also being available for sarilumab. International guidelines do include IL-6 inhibitors as one of the options available for severe or critically ill patients. There has been increased interest in evaluating these drugs with a series of clinical trials being registered and conducted in different countries. The level of investigation though perhaps needs to be further intensified as there is a need to focus on therapeutic options that can prove to be ‘life-saving’ as the number of COVID-19 fatalities worldwide keeps increasing alarmingly. IL-6 inhibitors could be one such treatment option, with generation of more evidence and completion of a larger number of systematic studies.

Background Although immune modulation is a promising therapeutic avenue in coronavirus disease 2019 (COVID-19), the most relevant targets remain to be found. COVID-19 has peculiar characteristics and outcomes, suggesting a unique immunopathogenesis. Methods Thirty-six immunocompetent non-COVID-19 and 27 COVID-19 patients with severe pneumonia were prospectively enrolled in a single center, most requiring intensive care. Clinical and biological characteristics (including T cell phenotype and function and plasma concentrations of 30 cytokines) and outcomes were compared. Results At similar baseline respiratory severity, COVID-19 patients required mechanical ventilation for significantly longer than non-COVID-19 patients (15 [7–22] vs. 4 (0–15) days; p = 0.0049). COVID-19 patients had lower levels of most classical inflammatory cytokines (G-CSF, CCL20, IL-1β, IL-2, IL-6, IL-8, IL-15, TNF-α, TGF-β), but higher plasma concentrations of CXCL10, GM-CSF and CCL5, compared to non-COVID-19 patients. COVID-19 patients displayed similar T-cell exhaustion to non-COVID-19 patients, but with a more unbalanced inflammatory/anti-inflammatory cytokine response (IL-6/IL-10 and TNF-α/IL-10 ratios). Principal component analysis identified two main patterns, with a clear distinction between non-COVID-19 and COVID-19 patients. Multivariate regression analysis confirmed that GM-CSF, CXCL10 and IL-10 levels were independently associated with the duration of mechanical ventilation. Conclusion We identified a unique cytokine response, with higher plasma GM-CSF and CXCL10 in COVID-19 patients that were independently associated with the longer duration of mechanical ventilation. These cytokines could represent the dysregulated immune response in severe COVID-19, as well as promising therapeutic targets. ClinicalTrials.gov: NCT03505281.

Objectives The purpose of this study is to test the safety and effectiveness of individually or simultaneously blocking IL-6, IL-6 receptor and IL-1 versus standard of care on blood oxygenation and systemic cytokine release syndrome in patients with COVID-19 coronavirus infection and acute hypoxic respiratory failure and systemic cytokine release syndrome. Trial design A phase 3 prospective, multi-center, interventional, open label, 6-arm 2x2 factorial design study. Participants Subjects will be recruited at the specialized COVID-19 wards and/or ICUs at 16 Belgian participating hospitals. Only adult (≥18y old) patients will be recruited with recent (≤16 days) COVID-19 infection and acute hypoxia (defined as PaO2/FiO2 below 350mmHg or PaO2/FiO2 below 280 on supplemental oxygen and immediately requiring high flow oxygen device or mechanical ventilation) and signs of systemic cytokine release syndrome characterized by high serum ferritin, or high D-dimers, or high LDH or deep lymphopenia or a combination of those, who have not been on mechanical ventilation for more than 24 hours before randomisation. Patients should have had a chest X-ray and/or CT scan showing bilateral infiltrates within the last 2 days before randomisation. Patients with active bacterial or fungal infection will be excluded. Intervention and comparator Patients will be randomized to 1 of 5 experimental arms versus usual care. The experimental arms consist of Anakinra alone (anti-IL-1 binding the IL-1 receptor), Siltuximab alone (anti-IL-6 chimeric antibody), a combination of Siltuximab and Anakinra, Tocilizumab alone (humanised anti-IL-6 receptor antibody) or a combination of Anakinra with Tocilizumab in addition to standard care. Patients treated with Anakinra will receive a daily subcutaneous injection of 100mg for a maximum of 28 days or until hospital discharge, whichever comes first. Siltuximab (11mg/kg) or Tocilizumab (8mg/kg, with a maximum dose of 800mg) are administered as a single intravenous injection immediately after randomization. Main outcomes The primary end point is the time to clinical improvement defined as the time from randomization to either an improvement of two points on a six-category ordinal scale measured daily till day 28 or discharge from the hospital or death. This ordinal scale is composed of (1) Death; (2) Hospitalized, on invasive mechanical ventilation or ECMO; (3) Hospitalized, on non-invasive ventilation or high flow oxygen devices; (4) Hospitalized, requiring supplemental oxygen; (5) Hospitalized, not requiring supplemental oxygen; (6) Not hospitalized. Randomisation Patients will be randomized using an Interactive Web Response System (REDCap). A 2x2 factorial design was selected with a 2:1 randomization regarding the IL-1 blockade (Anakinra) and a 1:2 randomization regarding the IL-6 blockade (Siltuximab and Tocilizumab). Blinding (masking) In this open-label trial neither participants, caregivers, nor those assessing the outcomes are blinded to group assignment. Numbers to be randomised (sample size) A total of 342 participants will be enrolled: 76 patients will receive usual care, 76 patients will receive Siltuximab alone, 76 patients will receive Tocilizumab alone, 38 will receive Anakinra alone, 38 patients will receive Anakinra and Siltuximab and 38 patients will receive Anakinra and Tocilizumab. Trial Status COV-AID protocol version 3.0 (15 Apr 2020). Participant recruitment is ongoing and started on April 4 th 2020. Given the current decline of the COVID-19 pandemic in Belgium, it is difficult to anticipate the rate of participant recruitment. Trial registration The trial was registered on Clinical Trials.gov on April 1st, 2020 ( ClinicalTrials.gov Identifier: NCT04330638) and on EudraCT on April 3rd 2020 (Identifier: 2020-001500-41). 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.

ObjectiveRecent clinical trials have demonstrated that colchicine may have metabolic and cardiovascular and benefits in at-risk patients; however, the mechanisms through which colchicine may improve outcomes are still unclear. We sought to examine colchicine’s effects on circulating inflammatory and metabolic molecules in adults with obesity and metabolic syndrome (MetS).MethodsBlood samples were collected pre- and post-intervention during a double-blind randomized controlled trial in which 40 adults with obesity and MetS were randomized to colchicine 0.6 mg or placebo twice-daily for 3 months. Serum samples were analyzed for 1305 circulating factors using the SomaScan Platform. The Benjamini–Hochberg procedure was used to adjust the false discovery rate (FDR) for multiple testing.ResultsAt baseline, age (48.0 ± 13.8 vs. 44.7 ± 10.3 years) and BMI (39.8 ± 6.4 vs. 41.8 ± 8.2 kg/m2) were not different between groups. After controlling for the FDR, 34 molecules were significantly changed by colchicine. Colchicine decreased concentrations of multiple inflammatory molecules, including C-reactive protein, interleukin 6, and resistin, in addition to vascular-related proteins (e.g., oxidized low-density lipoprotein receptor, phosphodiesterase 5A). Conversely, relative to placebo, colchicine significantly increased concentrations of eight molecules including secreted factors associated with metabolism and anti-thrombosis.ConclusionsIn adults with obesity, colchicine significantly affected concentrations of proteins involved in the innate immune system, endothelial function and atherosclerosis, uncovering new mechanisms behind its cardiometabolic effects. Further research is warranted to investigate whether colchicine’s IL-6 suppressive effects may be beneficial in COVID-19.

Objectives To investigates the effectiveness of curcumin-containing Nanomicelles as a therapeutic supplement in the treatment of patients with COVID-19 and its effect on immune responses balance changes following treatment. Trial design This study is conducted as a prospective, placebo-controlled with parallel group, single-center randomized clinical trial on COVID-19 patients. Participants Patients are selected from the COVID-19 ward of Shahid Mohammadi Hospital in Bandar Abbas, Iran. Inclusion criteria: 1. Real time PCR-approved positive COVID-19 test. 2. Both gender 3. Age between 18 and 75 years 4. Signing a written consent 5. Lack of participation in other clinical trials Exclusion criteria: 1. Pregnancy or lactation 2. Allergy to turmeric or curcumin 3. Smoking 4. Patient connected to the ventilator 5. SaO2 less than 90% or PaO2 less than 8 kPa 6. Having comorbidities (such as severe renal failure, Glomerular filtration rate less than 30 ml/min, liver failure, Congestive heart failure, or Chronic obstructive pulmonary disease) 7. History of gallstones 8. History of gastritis or active gastrointestinal ulcer Intervention and comparator In addition to the routine standard treatments for COVID-19, in the intervention group, 40mg nanomicelles containing curcumin (SinaCurcumin Capsule, Exir Nano Sina Company, Iran), four times per day (after breakfast, lunch, dinner and before bedtime) and in the placebo group as the control group, capsules with the same appearance and characteristics (Placebo capsules, Exir Nano Sina Company, Iran) are prescribed for two weeks. Main outcomes The effectiveness of Nano micelles containing curcumin treatment will be evaluated as daily clinical examinations of patients in both groups and, on days 0, 7 and 14, complete clinical symptoms and laboratory findings including peripheral blood and serum parameters such as inflammatory markers will be measured and recorded. Moreover, in order to evaluate the balance of immune responses changes following treatments, serum level of IFN-γ, IL-17, Il-4 and TGF-β serum cytokines will be measured in both groups at time points of 0, 7 and 14 days post treatment. Gene expression of t-bet, GATA-3, FoxP3 and ROR- γT will also be measured at mentioned time points to assess the shift of T helper1, T helper2, T regulatory and T helper 17 immune responses following treatment. Randomisation Randomized trials will be performed on 40 COVID-19 patients which will be randomized using encoded sealed boxes with computer generated random digits with 1:1 allocation ratio. In order to randomization, placebo and SinaCurcumin Capsules will be numbered first by computer generated random digits. SinaCurcumin and placebo will then be stored and numbered in sealed packages based on generated random numbers. Finally, according to the order in which patients enter the study, packages are given to patients based on their number. Blinding (masking) The present study will be blind for all patients, physicians and nurses, laboratory technicians and statisticians. Numbers to be randomised (sample size) A total of 40 patients will be included in the study, 20 of them will be randomly assigned to the intervention group and 20 to the placebo group. Trial status This is Version 1.0 of protocol dated 21 May 2020. The recruitment was started June 24, 2020 and is expected to be completed by October 31, 2020. Trial registration This present clinical trial has been registered in the Iranian Registry of Clinical Trials (IRCT) with the registration code of “IRCT20200611047735N1”, https://www.irct.ir/trial/48843 . Dated: 19 June 2020. 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.

Objectives Primary Objective • To evaluate the effect of ravulizumab, a long-acting complement (C5) inhibitor plus best supportive care (BSC) compared with BSC alone on the survival of patients with COVID-19. Secondary Objectives • Number of days free of mechanical ventilation at Day 29 • Duration of intensive care unit stay at Day 29 • Change from baseline in Sequential Organ Failure Assessment (SOFA) score at Day 29 • Change from baseline in peripheral capillary oxygen saturation/ fraction of inspired oxygen (SpO2 /FiO2) at Day 29 • Duration of hospitalization at Day 29 • Survival (based on all-cause mortality) at Day 60 and Day 90 Safety • Incidence of treatment-emergent adverse events and treatment-emergent serious adverse events. PK/PD/Immunogenicity • Change in serum ravulizumab concentrations over time • Change in serum free and total C5 concentrations over time • Incidence and titer of anti-ALXN1210 antibodies Biomarkers • Change in absolute level of soluble biomarkers in blood associated with complement activation, inflammatory processes, and hypercoagulable states over time Exploratory • Incidence of progression to renal failure requiring dialysis at Day 29 • Time to clinical improvement (based on a modified 6-point ordinal scale) over 29 days • SF-12 Physical Component Summary (PCS) and Mental Component Summary (MCS) scores at Day 29 (or discharge), Day 60, and Day 90 • EuroQol 5-dimension 5-level (EQ-5D-5L) scores at Day 29 (or discharge), Day 60, and Day 90 Trial design This is a multicenter Phase 3, open-label, randomized, controlled, study. The study is being conducted in acute care hospital settings in the United States, United Kingdom, Spain, France, Germany, and Japan. Participants Male or female patients at least 18 years of age, weighing ≥ 40 kg, admitted to a designated hospital facility for treatment will be screened for eligibility in this study. Key Inclusion criteria • Confirmed diagnosis of SARS-CoV-2 infection (eg, via polymerase chain reaction [PCR] and/or antibody test) presenting as severe COVID-19 requiring hospitalization • Severe pneumonia, acute lung injury, or ARDS confirmed by computed tomography (CT) or X-ray at Screening or within the 3 days prior to Screening, as part of the patient’s routine clinical care • Respiratory distress requiring mechanical ventilation, which can be either invasive (requiring endotracheal intubation) or non-invasive (with continuous positive airway pressure [CPAP] or bilevel positive airway pressure [BiPAP]) Key Exclusion criteria • Patient is not expected to survive for more than 24 hours • Patient is on invasive mechanical ventilation with intubation for more than 48 hours prior to Screening • Severe pre-existing cardiac disease (ie, NYHA Class 3 or Class 4, acute coronary syndrome, or persistent ventricular tachyarrhythmias) • Patient has an unresolved Neisseria meningitidis infection Excluded medications and therapies • Current treatment with a complement inhibitor • Intravenous immunoglobulin (IVIg) within 4 weeks prior to randomization on Day 1 Excluded prior/concurrent clinical study experience • Treatment with investigational therapy in a clinical study within 30 days before randomization, or within 5 half-lives of that investigational therapy, whichever is greater • Exceptions a. Investigational therapies will be allowed if received as part of best supportive care through an expanded access protocol or emergency approval for the treatment of COVID-19. b. Investigational antiviral therapies (such as remdesivir) will be allowed even if received as part of a clinical study. Intervention and comparator The study consists of a Screening Period of up to 3 days, a Primary Evaluation Period of 4 weeks, a final assessment at Day 29, and a Follow-up Period of 8 weeks. For patients randomized to ravulizumab plus BSC, a weight-based dose of ravulizumab (≥40 to < 60 kg/2400 mg, 60 to < 100 kg/2700 mg, ≥ 100 kg/3000 mg) will be administered on Day 1. On Day 5 and Day 10, additional doses of 600 mg (≥40 to <60 kg) or 900 mg (>60 kg) ravulizumab will be administered and on Day 15 patients will receive 900 mg ravulizumab. There is no active or placebo comparator in this open-label clinical trial. The total duration of each patient’s participation is anticipated to be approximately 3 months. Main outcomes The primary efficacy outcome of this study is survival (based on all-cause mortality) at Day 29. Randomisation Patients will be randomized in a 2:1 ratio (ravulizumab plus BSC:BSC alone). Randomization will be stratified by intubated or not intubated on Day 1. Computer-generated randomization lists will be prepared by a third party under the direction of the sponsor. Investigators, or designees, will enrol patients and then obtain randomization codes using an interactive voice/web response system. The block size will be kept concealed so that investigators cannot select patients for a particular treatment assignment. Blinding (masking): This is an open-label study. Numbers to be randomised (sample size): Approximately 270 patients will be randomly assigned in a 2:1 ratio to ravulizumab plus BSC (n=180) or BSC alone (n=90). Trial status Protocol Number: ALXN1210-COV-305 Original Protocol: 09 Apr 2020 Protocol Amendment 1 (Global): 13 Apr 2020 Protocol Amendment 2 (Global): 17 Apr 2020 Protocol Amendment 3 (Global): 09 Jun 2020 Recruitment is currently ongoing. Recruitment was initiated on 11 May 2020. We expect recruitment to be completed by 30 Nov 2020. Trial registration Clinicaltrials.gov: Protocol Registry Number: NCT04369469 ; First posted; 30 Apr 2020 EU Clinical Trials Register: EudraCT Number: https://www.clinicaltrialsregister.eu/ctr-search/search?query=ALXN1210-COV-305 , Start date: 07 May 2020 Full protocol The full redacted 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.

Here we show, in a double-blind, randomized, placebo-controlled trial in 37,107 fully immunized infants in Soweto, South Africa, that a 9-valent pneumococcal conjugate vaccine, PncCV, prevents 31% (95% confidence interval = 15–43%) of pneumonias associated with any of seven respiratory viruses in children in hospital. These data suggest that the pneumococcus has a major role in the development of pneumonia associated with these viruses and that viruses contribute to the pathogenesis of bacterial pneumonia.  NOTE: In the version of this article originally published online, the species name was misspelled Streptococcus pnemoniae in the title of the article. The name should be Streptococcus pneumoniae . This error has been corrected for the HTML and print versions of the article.

Objectives The BCG vaccine, widely used in Brazil in new-borns, induces adjuvant protection for several diseases, including childhood virus infections. BCG activates monocytes and innate memory NK cells which are crucial for the antiviral immune response. Therefore, strategies to prevent COVID-19 in health workers (HW) should be carried out to prevent them becoming unwell so that they can continue to work during the pandemic. The hypothesis is that BCG will improve the innate immune response and prevent symptomatic infection or COVID-19 severity. The primary objective is to verify the effectiveness and safety of the BCG vaccine to prevent or reduce incidence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in the city of Goiânia (Brazil) among HW previously vaccinated with BCG and also its severity and mortality during the pandemic of the disease. Secondary objectives are to estimate the incidence of COVID-19 among these professionals and the innate immune response elicited to BCG. Trial design This a phase II trial for repositioning BCG as a preventive strategy against COVID-19. The trial is an open-label, parallel-group randomised clinical trial, comparing HW vaccinated with BCG and HW not vaccinated. Participants The trial will recruit 800 HW of Goiânia - Goiás, Brazil to reach a total of 400 HW included after comorbidities questioning and laboratorial evaluation. Eligibility criteria: Any HW presenting BCG vaccination scar with direct contact with suspected COVID-19 patients for at least 8 hours per week, whether in hospital beds, ICU, or in transportation or admission (nurses, doctors, physiotherapists, nutritionists, receptionists, etc.) who have negative IgM and IgG COVID-19 test. Participants with any of the following characteristics will be excluded: - Have had in the last fifteen days any signs or symptoms of virus infection, including COVID-19; - Have had fever in the last fifteen days; - Have been vaccinated fifteen days before the inclusion; - Have a history or confirmation of any immunosuppressive disease such as HIV, presented solid tumour in the last two years or autoimmune diseases; - Are under preventive medication with antibiotics, steroid anti-inflammatories, or chemotherapy; - Have less than 500 neutrophils per mL of blood; - Have previously been diagnosed with tuberculosis; - Are breastfeeding or pregnant; - Are younger than 18 years old; - Are participating as an investigator in this clinical trial. Intervention and comparator HW will be randomized into the BCG vaccinated group or the BCG unvaccinated control group. The BCG vaccinated group will receive in the right arm, intradermally, a one off dose of 0.1 mL corresponding to approximately 2 x10 5 to 8 x10 5 CFU of live, freeze-dried, attenuated BCG Moscow 361-I, Bacillus Calmette Guerin vaccine (Serum Institute of India PVT. LTD.). The unvaccinated control group will not be vaccinated. The HW allocated in both groups will be followed up at specific times points until 180 days post inclusion. The vaccinated and control groups will be compared according to COVID-19 related outcomes. Main outcomes The primary outcomes are the incidence coefficient of infection by SARS-CoV-2 determined by RT-PCR of naso-oropharyngeal swab specimen or rapid lateral flow IgG and IgM test, and presence of general COVID-19 symptoms, disease severity and admission to hospital during the 180 days of follow up. The secondary outcome is the innate immune response elicited 15-20 days after vaccination. Randomisation The vaccine vial contains approximately 10 doses. In order to optimize the vaccine use, the randomisation was performed in blocks of 20 participants using the platform randomization.com [ http://www.jerrydallal.com/random/permute.htm ]. The randomization was prepared before any HW inclusion. The results were printed and inserted in sealed envelopes that were numbered with BCG-001 to BCG-400. The printed results as well the envelopes had the same numbers. At the time of the randomisation, each participant that meets the inclusion criteria will receive a consecutive participant number [BCG-001-BCG-400]. The sealed envelope with the assigned number, blinded to the researchers, will be opened in front of the participant and the arm allocation will be known. Blinding (masking) There is no masking for the participants or for the healthcare providers. The study will be blinded to the laboratory researchers and to those who will be evaluating the outcomes and performing the statistical analyses. In this case, only the participant identification number will be available. Numbers to be randomised (sample size) Four hundred heath workers will be randomised in two groups. Two hundred participants will be vaccinated, and 200 participants will not be vaccinated. Trial Status The protocol approved by the Brazilian Ethical Committee is the seventh version, number CAAE: 31783720.0.0000.5078. The trial has been recruiting since September 20 th , 2020. The clinical trial protocol was registered on August 5 th , 2020. It is estimated that recruitment will finish by March 2021. Trial registration The protocol number was registered on August 5 th , 2020 at REBEC (Registro Brasileiro de Ensaios Clínicos). Register number: RBR-4kjqtg and WHO trial registration number UTN: U1111-1256-3892. 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.