Hi everyone, I am 74 years old, have ET, Jak2 and exon12 negative. I have been on interferon 2a for 2 1/2 years and am sick of having painful legs and lower back. My bloods are normal, platelets 250-300. I would like to stop the meds but haem is reluctant. Would there be any point in switching to Pegasys? I am hoping to have fewer side effects/less pain, so does anyone know if this is likely? How differently does Pegasys work compared with interferon 2a? How long does each stay in the body? Does anyone know, or can anyone ask someone who knows? Imagine going for a walk without legs hurting and going to sleep without pain stabs. I take paracetamol with my injection at night and it helps, but any exercise, including just ordinary walking, aggravates the pain.