In a recent systematic review and meta-analysis of IFN (both peg and non-peg) treated patients with PV or ET [108], 44 studies including 1359 patients were analyzed; complete hematologic response rate in PV was reported at 49% with no difference between peg- and non-peg-IFN preparations; annualized rates of thrombotic complications and treatment discontinuation in patients with PV were estimated at 0.5% and 6.5%, respectively [108]. Here, IFNA1 is linked to acquired polycythemia vera.