I definitely does not have anything to do with covid or the shot or a blood transfusion. I was diagnosed after covid & I did not take any of the vaccines & I have never had a blood transfusion. My hematologist said they dont know why the mutation happens & that it's typically caught in older adults because they typically get more blood work done than younger adults. Im only 48 & was diagnosis with ET Jak 12 positive at 47. It was caught on a random blood test that I had done. My levels when 1st diagnosed were around 780's. Im not on anything but baby aspirin for now due to my low risk of blood clots & no history of them. I take plenty of other vitamins daily & my levels have been staying around 630's -670's. I was told I probably have had it for several yrs. before it actually started causing symptoms & increased levels. I thought the symptoms were being caused by being in peri menopause since some are the same. I also started having lots of migraines almost daily to the point I was out on a preventive medication about 10 yrs.ago. Who knows, that could have been when it happened since headaches are one of the symptoms. Hope this helps.