My wife who is 74 has no history of anemia and sees the doctor quarterly with semi annual blood tests due to type II diabetes. She had 3 Pfizer COVID vaccine inoculations. She suddenly was very tired and was severely anemic and the doctor suspected internal bleeding. She had upper and lower endoscopy and the intestinal camera. All were negative. She is now no longer anemic after taking significant iron supplements
. Her 70 year old female friend had the same experience as well as another female friend.
Anemia is detected by a blood test and you may have it but not know it until you have the specific blood test. I believe anemia after the vaccines is far more common but the full extent is not known due to the need for a blood test to confirm.