 The Low-PV study is a multicenter, phase II, randomized trial aimed to assess whether the addition of Pegylated Proline-interferon-alpha-2b to the best therapeutic current strategy available based on phlebotomies and low dose acetylsalicylic acid ASA could improve the efficacy of treatment of patients with PV at low risk of thrombosis younger than 60 years and without prior vascular events, in term of control of recommended level of hematocrit 45, over a period of 12 months. 