 Specific polysaccharide antibody deficiency SPAD is a primary immunodeficiency characterized by a deficient antibody production to capsular polysaccharides with normal total immunoglobulin levels. Patients suffer from recurrent ear-nose and throat infections and lung infections. SPAD can also occur as part of a primary immunodeficiency affecting other components of the immune system. Diagnosis of SPAD is hampered by difficulties with the interpretation of the Pneumovax 23 antibody response. The purpose of this study is to assess the diagnostic value of the Typhim Vi antibody response and allohemagglutinin titers as an alternative to the Pneumovax 23 response to detect polysaccharide specific antibody deficiency. 