- Impaired immune function or chronic infections including (but not limited to) HIV, hepatitis B or C, tuberculosis, organ transplant, cancer, current and or expected receipt of chemotherapy, radiation therapy, steroids [i.e., > 20 mg of prednisone given daily or on alternative days for 2 weeks or more in the past 90 days*); (nasal and topical steroids are allowed)],antitumor necrosis factor agents, or any other immunosuppressive therapy, anatomic or functional asplenia, congenital immunodeficiency.