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Risk Factors

Haemophilus influenzae, including Hib, is a bacterium that can cause a severe infection, occurring mostly in infants and children younger than five years of age. Adults 65 years and older are also at higher risk. American Indian/Alaska Native populations are also at increased risk for invasive Haemophilus influenzae disease.

People with certain medical conditions are at higher risk for developing a Haemophilus influenzae infection. Those medical conditions include:

  • Sickle cell disease
  • Asplenia (no spleen)
  • HIV (human immunodeficiency virus) infection
  • Antibody and complement deficiency syndromes
  • Receipt of chemotherapy or radiation therapy for malignant neoplasms
  • Receipt of hematopoietic stem cell transplant
This bar chart describes estimated U.S. incidence of Haemophilus influenzae by age-group from 2001 to 2012.
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