 Even though IFN-alpha has shown its activity in PV in the 1980s, it is still considered as an experimental treatment in Europe due to pending approval in this indication Barbui et al, 2011. It induces major or complete molecular remissions in patients with PV accompanied by a reduction in the risk of thrombosis and bleeding - the major determinants of morbidity in this indication Hasselbalch, 2011. However, only low doses are tolerated and significant adverse effects from long-term use may limit its usefulness. 