What are the risk factors for invasive Hib disease?

People with certain immunocompromising conditions are considered at increased risk for invasive Hib disease. These conditions include functional or anatomic asplenia, HIV infection, immunoglobulin deficiency including immunoglobulin G2 subclass deficiency, early component complement deficiency, receipt of a hematopoietic stem cell transplant, or receipt of chemotherapy or radiation therapy for treatment of cancer.