- Immunocompromised patients including, but not limited to: patients with known HIV infection (CD4 + <200/mm3); known neutropenia (<1500 neutrophils/mm3); chronic corticosteroid therapy (≥ 10mg/day prednisolone equivalent during at least three months); immunodepressant treatment within the previous six months; splenectomized patients or patients with known hyposplenia or asplenia.