MPL and COVID-19: Some cases of AA after COVID-19 vaccination recovered without treatment, but in most cases, various treatments, including blood transfusion, use of cyclosporine, thrombopoietin receptor agonists, rabbit anti-thymocyte globulin, corticosteroid, and granulocyte colony-stimulating factor and allogeneic hematopoietic stem cell transplantation, were needed [6–11].