I have wondered the same about my iron level and Covid vaccine. My hemoglobin level would come back up every time with oral iron and my doctor would tell me to stop taking iron “it’s not good to take iron all the time”. After my first Pfizer vaccine in January, 2021 and subsequent boosters it has not come back up with oral iron and 5 iron infusions. She referred me to hematologist in September and I was diagnosed with Waldenstrom’s. Did Covid vaccine “turn on” genotype (if this is correct word?).