Severe respiratory failure and multi-organ damage in coronavirus disease 2019 (COVID-19) patients have not a unitary pathophysiological interpretation. There is evidence of an association between the clinical entity of the disease and its severity with the plasma levels of D-dimer and inflammatory indexes. On the basis of retrospective investigations there is accumulating evidence of alterations in the haemostatic parameters that with increased D-dimer values, increased coagulation time and platelets may be predictors of worse prognosis. A systematic survey conducted in the coronavirus disease 2019 (COVID-19) Centre of the AOUI Verona, as part of the Database and Study on the role of platelets in the clinical manifestations of COVID-19 (Ethics Committee CESC Verona and Rovigo approved) revealed by means of computerized tomography (CT) angiograph in patients with a persistent respiratory deficit and very high D-dimer values mainly multiple, bilateral vascular occlusions involving the segmental and subsegmental branches of the pulmonary arteries. This finding is suggestive of a frequent and clinically relevant thrombotic process in a appreciable number (approximately 20%) of patients with COVID-19 pneumonia hospitalized in medical wards. It is a well-established clinical notion that acute and chronic inflammatory diseases may favour the onset of venous thromboembolic events in hospitalized patients. Thromboprophylaxis with a fixed dose of heparin/low molecular weight heparin (LMWH) is recommended for medical patient with concomitant neoplasia or inflammatory disease. It is conceivable that under conditions, such as SARS-CoV2 pneumonia, an inflammation-dependent thrombotic process takes place and that platelet activation may play a pathogenic role both in the thrombotic process and in the amplification of the inflammatory process. In fact, there is experimental evidence that platelet activation in inflammation would lead to accelerated coagulation and a thrombotic vascular occlusion, with similarities to what is widely documented in atherothrombosis and thrombotic microangiopathies. The administration of antiplatelet drugs represents the cornerstone for the prevention and treatment of arterial thromboembolism in atherosclerotic disease and has also shown some limited efficacy also in the context of venous and arterial thromboembolism associated with atrial fibrillation. The use of acetylsalicylic acid may improve inflammation and respiratory function in humans as indicated by the results of observational studies. There are currently no validated protocols for thrombosis prevention in the field of pulmonary viral diseases, in particular COVID-19. There is scientific rationale to consider acetylsalicylic acid for the prevention of thrombosis in the pulmonary circulation and attenuation of inflammation. This is supported by numerous demonstrations of the anti-inflammatory activity of antiplatelet agents and the evidence of improvement in respiratory function both in human and experimental pathology. A retrospective observational study showed that patients with COVID-19 pneumonia treated with acetyl salicylic acid had a lower incidence of progression to respiratory failure requiring mechanical ventilation, without evidence of increased incidence of bleeding complications. The hypothesis underlying the present study project is that in Covid-19 platelet activation occurs via an inflammation-dependent mechanism and that early antithrombotic prophylaxis in non-critical patients, like those admitted to medical wards, could reduce the incidence of pulmonary thrombosis as well as respiratory and multi-organ failure, contributing to improve clinical outcome of the patients with pneumonia caused by SARS-CoV2 viruses. The anticoagulant activity exerted by a fixed dose of enoxaparin (4000U/day), recommended in patients with the described clinical features, according to a note of the "Italian Medicines Agency" (AIFA), together with the prevention of thrombogenic activity of platelets by acetylsalicylic acid could prevent aggravation of COVID-19 patients to a greater extent than enoxaparin alone given at the same dose. Early initiation of treatment should mitigate the presentation of pneumonia. The proposed treatment is feasible in all coronavirus disease 2019 (COVID-19) patients, regardless of the treatment regimen (antivirals, anti-inflammatory drugs), except for specific contraindications. To this aim, it was designed a randomised, placebo-controlled, double blind, parallel arms study to investigate the potential protection of acetylsalicylic acid towards the progression of lung failure in patients admitted to a medical ward for SARS-CoV-2 pneumonia. A 15-day treatment period is considered. Primary endpoint is the occurrence of one of the following events: admission to an intensive care unit, requirement of mechanical ventilation, PaO2/FiO2 less than 150 mm Hg.