Inclusion Criteria:  Patients with diagnosis of PV or ET or PreMF according to WHO or BSCH criteria (bone marrow biopsy not compulsory). Patients with JAK2V617F mutation (threshold allele burden > 1%).  Patients considered as "high-risk" patients:  based on age (> 60-year-old) based on thrombotic history (compatible with antithrombotic randomization) but aged ≥ 18-year-old. Length of time from MPN diagnostic to inclusion will not exceed 12 months.  Exclusion Criteria:  Contra-indication to aspirin or DOAC due to allergic situation or recent history of major bleeding. Formal indication of treatment with aspirin or DOAC (thus precluding randomization). Inability to give informed consent. Patients under curatorship/guardianship Concomitant use of a strong inhibitor or inducer of CYP3A4 (like ruxolitinib). Chronic liver disease or chronic hepatitis. Renal insufficiency with creatinine <30 ml/mn on Cockcroft and Gault Formula Patient considered at high-risk of bleeding: patients with current or recent major or clinical relevant non major bleeding gastrointestinal or cerebral bleedings Planned pregnancy within 24 months No appropriate contraception (estrogen contraception or no contraception) in women of childbearing age or breastfeeding woman PS>2 or life expectancy <12 months.