1. patients \<18 years old; 2. hospitalization indication upon first medical care; 3. positive test for influenza in the first visit; 4. any known liver disease associated with coagulopathy; inr (international normalized ratio) \> 1.5; 5. pregnant, lactating or with the possibility of becoming pregnant and without using an adequate contraceptive method; 6. high risk of bleeding; history of bronchiectasis or pulmonary cavitation, significant bleeding in the last 3 months, active gastroduodenal ulcer, history of recent bleeding (within 3 months) or a high risk of bleeding; 7. stroke within 1 month or any history of hemorrhagic or lacunar stroke or any intracranial bleeding or any intracranial neoplasia, brain metastasis, arteriovenous malformation or brain aneurysm; 8. severe heart failure with left ventricular ejection fraction \<30% (echocardiogram or other validated method previously documented) or symptoms of heart failure class iii or iv of the new york heart association (nyha); 9. estimated glomerular filtration rate (egfr) \<30 ml / min; 10. clinical indication for dual antiplatelet therapy or anticoagulation therapy (vte, atrial fibrillation / flutter, mechanical valve prosthesis); 11. marked thrombocytopenia (platelets \<50,000 / mm3); 12. non-cardiovascular disease that is associated with a poor prognosis, for example, active cancer (excluding non-melanoma skin cancer) defined as cancer without remission or requiring active chemotherapy or adjuvant therapies such as immunotherapy or radiation therapy or that increases the risk of an adverse reaction to the evaluated interventions; 13. history of hypersensitivity or known contraindication to rivaroxaban; 14. systemic treatment with strong inhibitors of cytochrome p450 3a4 (cyp3a4) and glycoprotein p (pgp) (for example, systemic azole antimycotics, such as ketoconazole and human immunodeficiency virus \[hiv\] protein inhibitors, such as ritonavir) or strong inducers of cyp 3a4, that is, rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine; 15. current treatment being tested; 16. concomitant participation in another study with experimental drugs in the context of covid; 17. use of chloroquine or hydroxychloroquine associated with azithromycin; 18. active cancer; 19. other contraindications to rivaroxaban;

1. patients \<18 years old; 2. hospitalization indication upon first medical care; 3. positive test for influenza in the first visit; 4. any known liver disease associated with coagulopathy; inr (international normalized ratio) \> 1.5; 5. pregnant, lactating or with the possibility of becoming pregnant and without using an adequate contraceptive method; 6. high risk of bleeding; history of bronchiectasis or pulmonary cavitation, significant bleeding in the last 3 months, active gastroduodenal ulcer, history of recent bleeding (within 3 months) or a high risk of bleeding; 7. stroke within 1 month or any history of hemorrhagic or lacunar stroke or any intracranial bleeding or any intracranial neoplasia, brain metastasis, arteriovenous malformation or brain aneurysm; 8. severe heart failure with left ventricular ejection fraction \<30% (echocardiogram or other validated method previously documented) or symptoms of heart failure class iii or iv of the new york heart association (nyha); 9. estimated glomerular filtration rate (egfr) \<30 ml / min; 10. clinical indication for dual antiplatelet therapy or anticoagulation therapy (vte, atrial fibrillation / flutter, mechanical valve prosthesis); 11. marked thrombocytopenia (platelets \<50,000 / mm3); 12. non-cardiovascular disease that is associated with a poor prognosis, for example, active cancer (excluding non-melanoma skin cancer) defined as cancer without remission or requiring active chemotherapy or adjuvant therapies such as immunotherapy or radiation therapy or that increases the risk of an adverse reaction to the evaluated interventions; 13. history of hypersensitivity or known contraindication to rivaroxaban; 14. systemic treatment with strong inhibitors of cytochrome p450 3a4 (cyp3a4) and glycoprotein p (pgp) (for example, systemic azole antimycotics, such as ketoconazole and human immunodeficiency virus \[hiv\] protein inhibitors, such as ritonavir) or strong inducers of cyp 3a4, that is, rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine; 15. current treatment being tested; 16. concomitant participation in another study with experimental drugs in the context of covid; 17. use of chloroquine or hydroxychloroquine associated with azithromycin; 18. active cancer; 19. other contraindications to rivaroxaban;

patients <18 years old; hospitalization indication upon first medical care; positive test for influenza in the first visit; any known liver disease associated with coagulopathy; inr (international normalized ratio) > 1.5; pregnant, lactating or with the possibility of becoming pregnant and without using an adequate contraceptive method; high risk of bleeding; history of bronchiectasis or pulmonary cavitation, significant bleeding in the last 3 months, active gastroduodenal ulcer, history of recent bleeding (within 3 months) or a high risk of bleeding; stroke within 1 month or any history of hemorrhagic or lacunar stroke or any intracranial bleeding or any intracranial neoplasia, brain metastasis, arteriovenous malformation or brain aneurysm; severe heart failure with left ventricular ejection fraction <30% (echocardiogram or other validated method previously documented) or symptoms of heart failure class iii or iv of the new york heart association (nyha); estimated glomerular filtration rate (egfr) <30 ml / min; clinical indication for dual antiplatelet therapy or anticoagulation therapy (vte, atrial fibrillation / flutter, mechanical valve prosthesis); marked thrombocytopenia (platelets <50,000 / mm3); non-cardiovascular disease that is associated with a poor prognosis, for example, active cancer (excluding non-melanoma skin cancer) defined as cancer without remission or requiring active chemotherapy or adjuvant therapies such as immunotherapy or radiation therapy or that increases the risk of an adverse reaction to the evaluated interventions; history of hypersensitivity or known contraindication to rivaroxaban; systemic treatment with strong inhibitors of cytochrome p450 3a4 (cyp3a4) and glycoprotein p (pgp) (for example, systemic azole antimycotics, such as ketoconazole and human immunodeficiency virus [hiv] protein inhibitors, such as ritonavir) or strong inducers of cyp 3a4, that is, rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine; current treatment being tested; concomitant participation in another study with experimental drugs in the context of covid; use of chloroquine or hydroxychloroquine associated with azithromycin; active cancer; other contraindications to rivaroxaban;

patients <18 years old; hospitalization indication upon first medical care; positive test for influenza in the first visit; any known liver disease associated with coagulopathy; inr (international normalized ratio) > 1.5; pregnant, lactating or with the possibility of becoming pregnant and without using an adequate contraceptive method; high risk of bleeding; history of bronchiectasis or pulmonary cavitation, significant bleeding in the last 3 months, active gastroduodenal ulcer, history of recent bleeding (within 3 months) or a high risk of bleeding; stroke within 1 month or any history of hemorrhagic or lacunar stroke or any intracranial bleeding or any intracranial neoplasia, brain metastasis, arteriovenous malformation or brain aneurysm; severe heart failure with left ventricular ejection fraction <30% (echocardiogram or other validated method previously documented) or symptoms of heart failure class iii or iv of the new york heart association (nyha); estimated glomerular filtration rate (egfr) <30 ml / min; clinical indication for dual antiplatelet therapy or anticoagulation therapy (vte, atrial fibrillation / flutter, mechanical valve prosthesis); marked thrombocytopenia (platelets <50,000 / mm3); non-cardiovascular disease that is associated with a poor prognosis, for example, active cancer (excluding non-melanoma skin cancer) defined as cancer without remission or requiring active chemotherapy or adjuvant therapies such as immunotherapy or radiation therapy or that increases the risk of an adverse reaction to the evaluated interventions; history of hypersensitivity or known contraindication to rivaroxaban; systemic treatment with strong inhibitors of cytochrome p450 3a4 (cyp3a4) and glycoprotein p (pgp) (for example, systemic azole antimycotics, such as ketoconazole and human immunodeficiency virus [hiv] protein inhibitors, such as ritonavir) or strong inducers of cyp 3a4, that is, rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine; current treatment being tested; concomitant participation in another study with experimental drugs in the context of covid; use of chloroquine or hydroxychloroquine associated with azithromycin; active cancer; other contraindications to rivaroxaban;

1. patients <18 years old; 2. hospitalization indication upon first medical care; 3. positive test for influenza in the first visit; 4. any known liver disease associated with coagulopathy; inr (international normalized ratio) > 1.5; 5. pregnant, lactating or with the possibility of becoming pregnant and without using an adequate contraceptive method; 6. high risk of bleeding; history of bronchiectasis or pulmonary cavitation, significant bleeding in the last 3 months, active gastroduodenal ulcer, history of recent bleeding (within 3 months) or a high risk of bleeding; 7. stroke within 1 month or any history of hemorrhagic or lacunar stroke or any intracranial bleeding or any intracranial neoplasia, brain metastasis, arteriovenous malformation or brain aneurysm; 8. severe heart failure with left ventricular ejection fraction <30% (echocardiogram or other validated method previously documented) or symptoms of heart failure class iii or iv of the new york heart association (nyha); 9. estimated glomerular filtration rate (egfr) <30 ml / min; 10. clinical indication for dual antiplatelet therapy or anticoagulation therapy (vte, atrial fibrillation / flutter, mechanical valve prosthesis); 11. marked thrombocytopenia (platelets <50,000 / mm3); 12. non-cardiovascular disease that is associated with a poor prognosis, for example, active cancer (excluding non-melanoma skin cancer) defined as cancer without remission or requiring active chemotherapy or adjuvant therapies such as immunotherapy or radiation therapy or that increases the risk of an adverse reaction to the evaluated interventions; 13. history of hypersensitivity or known contraindication to rivaroxaban; 14. systemic treatment with strong inhibitors of cytochrome p450 3a4 (cyp3a4) and glycoprotein p (pgp) (for example, systemic azole antimycotics, such as ketoconazole and human immunodeficiency virus [hiv] protein inhibitors, such as ritonavir) or strong inducers of cyp 3a4, that is, rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine; 15. current treatment being tested; 16. concomitant participation in another study with experimental drugs in the context of covid; 17. use of chloroquine or hydroxychloroquine associated with azithromycin; 18. active cancer; 19. other contraindications to rivaroxaban;

1. patients <18 years old; 2. hospitalization indication upon first medical care; 3. positive test for influenza in the first visit; 4. any known liver disease associated with coagulopathy; inr (international normalized ratio) > 1.5; 5. pregnant, lactating or with the possibility of becoming pregnant and without using an adequate contraceptive method; 6. high risk of bleeding; history of bronchiectasis or pulmonary cavitation, significant bleeding in the last 3 months, active gastroduodenal ulcer, history of recent bleeding (within 3 months) or a high risk of bleeding; 7. stroke within 1 month or any history of hemorrhagic or lacunar stroke or any intracranial bleeding or any intracranial neoplasia, brain metastasis, arteriovenous malformation or brain aneurysm; 8. severe heart failure with left ventricular ejection fraction <30% (echocardiogram or other validated method previously documented) or symptoms of heart failure class iii or iv of the new york heart association (nyha); 9. estimated glomerular filtration rate (egfr) <30 ml / min; 10. clinical indication for dual antiplatelet therapy or anticoagulation therapy (vte, atrial fibrillation / flutter, mechanical valve prosthesis); 11. marked thrombocytopenia (platelets <50,000 / mm3); 12. non-cardiovascular disease that is associated with a poor prognosis, for example, active cancer (excluding non-melanoma skin cancer) defined as cancer without remission or requiring active chemotherapy or adjuvant therapies such as immunotherapy or radiation therapy or that increases the risk of an adverse reaction to the evaluated interventions; 13. history of hypersensitivity or known contraindication to rivaroxaban; 14. systemic treatment with strong inhibitors of cytochrome p450 3a4 (cyp3a4) and glycoprotein p (pgp) (for example, systemic azole antimycotics, such as ketoconazole and human immunodeficiency virus [hiv] protein inhibitors, such as ritonavir) or strong inducers of cyp 3a4, that is, rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine; 15. current treatment being tested; 16. concomitant participation in another study with experimental drugs in the context of covid; 17. use of chloroquine or hydroxychloroquine associated with azithromycin; 18. active cancer; 19. other contraindications to rivaroxaban;