I posted a while back on this thread and thought I'd give an update. After getting Covid in March '21, I had ongoing daily fevers (usu 100 and 101), terrible headaches, fatigue, and shortness of breath. I thought I was fighting a severe, extended case of long Covid. I went to Mayo at the end of June, and they discovered that I hadn't formed any antibodies to Covid-19. At that time, my d-dimer was elevated, too, so they were concerned about clots. Fortunately, my lungs had no clots, just evidence of Covid. I was admitted and given convalescent plasma and Remdesivir for treatment. I am now so much better. I had been treated with Rituxan (as a post-stem cell transplant treatment for lymphoma) up through last fall, and it most likely has interfered with my antibody production, even though I had had the Covid-19 vaccine in Dec/Jan '21 and acquired the virus in March. I am still very tired after exercise, and my lungs/breathing have a long way to go. But my fevers are gone, and I am so thankful for Mayo's doctors. I thought others might benefit from knowing that sometimes we don't form our own antibodies- if you've had cancer treatment, you may want to have your antibodies checked. I don't understand why my local infectious disease doc didn't check mine back in April, when I asked her about it...I suffered needlessly for 2.5 more months because of that. My recovery is slow-going, but I can tell I am at least making progress! Thank God for the good people who donate plasma/blood! I wish you all improved health, and I sure can empathize with what you are going through! Covid-19 stinks to high heaven.