participants are excluded from the study if any of the following criteria apply: - currently hospitalized or under immediate consideration for hospitalization at screening and day 1 - have new onset shortness of breath or increased shortness of breath from pre-covid-19 (for people with known copd) at screening and day 1 - hypoxemia (oxygen saturation <94% in ambient air or oxygen saturation below pre-covid-19 level for people with known copd) at day 1 - require supplemental oxygen (new requirement or increase in requirement from pre-covid-19 condition) at screening and day 1 - have a history of (in the past 3 months) or current active pathological bleeding - have a history of hemorrhagic stroke or intracranial hemorrhage - have a recent severe head trauma within 30 days which includes concussion, skull fracture or hospitalization for head injury - have known intracranial neoplasm, cerebral metastases, arteriovenous malformation or aneurysm - have history of pregnancy-related hemorrhage - have active gastroduodenal ulcer or other gastrointestinal bleeding diagnosed in the past 3 months - currently are in a hemodynamically unstable state - currently require thrombolysis or pulmonary embolectomy - have history of severe hypersensitivity reaction to xarelto® - currently have a prosthetic heart valve - have known diagnosis of triple positive antiphospholipid syndrome - have known diagnosis of chronic kidney disease (stage iv or receiving dialysis) - have a history of thrombocytopenia or known platelet count <100,000 cells/mm^3 - have history of bronchiectasis and pulmonary cavitation - have active cancer (e.g, receiving chemotherapy or treatment for complication of the active cancer) - had epidural or neuraxial anesthesia or spinal puncture in the past 2 weeks and plan to undergo these procedures during the study - had surgery in the past 4 weeks or plan to undergo surgery during the study - currently is pregnant or plans to become pregnant - currently is breastfeeding - share household with an enrolled participant in this study - co-enrollment in any clinical trial that includes prohibited procedures (spinal puncture or surgery) or that includes treatments within the same drug class as rivaroxaban or treatments for which co-administration with rivaroxaban are prohibited. note that any co-enrollment other than this requires approval by the sponsor. for any co-enrolled study, the total volume of blood samples collected across the studies should not exceed 275 milliliters (ml) in 4 weeks. - currently using and plan to use the following medications during the study - rivaroxaban or drugs in the same class - dual anti-platelets therapy - other anticoagulants - combined permeability glycoprotein (p-gp) and cytochrome p450 3a (cyp3a) inhibitors and inducers

participants are excluded from the study if any of the following criteria apply: - currently hospitalized or under immediate consideration for hospitalization at screening and day 1 - have new onset shortness of breath or increased shortness of breath from pre-covid-19 (for people with known copd) at screening and day 1 - hypoxemia (oxygen saturation <94% in ambient air or oxygen saturation below pre-covid-19 level for people with known copd) at day 1 - require supplemental oxygen (new requirement or increase in requirement from pre-covid-19 condition) at screening and day 1 - have a history of (in the past 3 months) or current active pathological bleeding - have a history of hemorrhagic stroke or intracranial hemorrhage - have a recent severe head trauma within 30 days which includes concussion, skull fracture or hospitalization for head injury - have known intracranial neoplasm, cerebral metastases, arteriovenous malformation or aneurysm - have history of pregnancy-related hemorrhage - have active gastroduodenal ulcer or other gastrointestinal bleeding diagnosed in the past 3 months - currently are in a hemodynamically unstable state - currently require thrombolysis or pulmonary embolectomy - have history of severe hypersensitivity reaction to xarelto® - currently have a prosthetic heart valve - have known diagnosis of triple positive antiphospholipid syndrome - have known diagnosis of chronic kidney disease (stage iv or receiving dialysis) - have a history of thrombocytopenia or known platelet count <100,000 cells/mm^3 - have history of bronchiectasis and pulmonary cavitation - have active cancer (e.g, receiving chemotherapy or treatment for complication of the active cancer) - had epidural or neuraxial anesthesia or spinal puncture in the past 2 weeks and plan to undergo these procedures during the study - had surgery in the past 4 weeks or plan to undergo surgery during the study - currently is pregnant or plans to become pregnant - currently is breastfeeding - share household with an enrolled participant in this study - co-enrollment in any clinical trial that includes prohibited procedures (spinal puncture or surgery) or that includes treatments within the same drug class as rivaroxaban or treatments for which co-administration with rivaroxaban are prohibited. note that any co-enrollment other than this requires approval by the sponsor. for any co-enrolled study, the total volume of blood samples collected across the studies should not exceed 275 milliliters (ml) in 4 weeks. - currently using and plan to use the following medications during the study - rivaroxaban or drugs in the same class - dual anti-platelets therapy - other anticoagulants - combined permeability glycoprotein (p-gp) and cytochrome p450 3a (cyp3a) inhibitors and inducers

participants are excluded from the study if any of the following criteria apply: - currently hospitalized or under immediate consideration for hospitalization at screening and day 1 - have new onset shortness of breath or increased shortness of breath from pre-covid-19 (for people with known copd) at screening and day 1 - hypoxemia (oxygen saturation <94% in ambient air or oxygen saturation below pre-covid-19 level for people with known copd) at day 1 - require supplemental oxygen (new requirement or increase in requirement from pre-covid-19 condition) at screening and day 1 - have a history of (in the past 3 months) or current active pathological bleeding - have a history of hemorrhagic stroke or intracranial hemorrhage - have a recent severe head trauma within 30 days which includes concussion, skull fracture or hospitalization for head injury - have known intracranial neoplasm, cerebral metastases, arteriovenous malformation or aneurysm - have history of pregnancy-related hemorrhage - have active gastroduodenal ulcer or other gastrointestinal bleeding diagnosed in the past 3 months - currently are in a hemodynamically unstable state - currently require thrombolysis or pulmonary embolectomy - have history of severe hypersensitivity reaction to xarelto® - currently have a prosthetic heart valve - have known diagnosis of triple positive antiphospholipid syndrome - have known diagnosis of chronic kidney disease (stage iv or receiving dialysis) - have a history of thrombocytopenia or known platelet count <100,000 cells/mm^3 - have history of bronchiectasis and pulmonary cavitation - have active cancer (e.g, receiving chemotherapy or treatment for complication of the active cancer) - had epidural or neuraxial anesthesia or spinal puncture in the past 2 weeks and plan to undergo these procedures during the study - had surgery in the past 4 weeks or plan to undergo surgery during the study - currently is pregnant or plans to become pregnant - currently is breastfeeding - share household with an enrolled participant in this study - co-enrollment in any clinical trial that includes prohibited procedures (spinal puncture or surgery) or that includes treatments within the same drug class as rivaroxaban or treatments for which co-administration with rivaroxaban are prohibited. note that any co-enrollment other than this requires approval by the sponsor. for any coenrolled study, the total volume of blood samples collected across the studies should not exceed 275 milliliters (ml) in 4 weeks. - currently using and plan to use the following medications during the study - rivaroxaban or drugs in the same class - dual anti-platelets therapy - other anticoagulants - combined permeability glycoprotein (p-gp) and cytochrome cyp3a inhibitors and inducers

participants are excluded from the study if any of the following criteria apply: - currently hospitalized or under immediate consideration for hospitalization at screening and day 1 - have new onset shortness of breath or increased shortness of breath from pre-covid-19 (for people with known copd) at screening and day 1 - hypoxemia (oxygen saturation <94% in ambient air or oxygen saturation below pre-covid-19 level for people with known copd) at day 1 - require supplemental oxygen (new requirement or increase in requirement from pre-covid-19 condition) at screening and day 1 - have a history of (in the past 3 months) or current active pathological bleeding - have a history of hemorrhagic stroke or intracranial hemorrhage - have a recent severe head trauma within 30 days which includes concussion, skull fracture or hospitalization for head injury - have known intracranial neoplasm, cerebral metastases, arteriovenous malformation or aneurysm - have history of pregnancy-related hemorrhage - have active gastroduodenal ulcer or other gastrointestinal bleeding diagnosed in the past 3 months - currently are in a hemodynamically unstable state - currently require thrombolysis or pulmonary embolectomy - have history of severe hypersensitivity reaction to xarelto® - currently have a prosthetic heart valve - have known diagnosis of triple positive antiphospholipid syndrome - have known diagnosis of chronic kidney disease (stage iv or receiving dialysis) - have a history of thrombocytopenia or known platelet count <100,000 cells/mm^3 - have history of bronchiectasis and pulmonary cavitation - have active cancer (e.g, receiving chemotherapy or treatment for complication of the active cancer) - had epidural or neuraxial anesthesia or spinal puncture in the past 2 weeks and plan to undergo these procedures during the study - had surgery in the past 4 weeks or plan to undergo surgery during the study - currently is pregnant or plans to become pregnant - currently is breastfeeding - share household with an enrolled participant in this study - co-enrollment in any clinical trial that includes prohibited procedures (spinal puncture or surgery) or that includes treatments within the same drug class as rivaroxaban or treatments for which co-administration with rivaroxaban are prohibited. note that any co-enrollment other than this requires approval by the sponsor. for any coenrolled study, the total volume of blood samples collected across the studies should not exceed 275 milliliters (ml) in 4 weeks. - currently using and plan to use the following medications during the study - rivaroxaban or drugs in the same class - dual anti-platelets therapy - other anticoagulants - combined permeability glycoprotein (p-gp) and cytochrome cyp3a inhibitors and inducers