Evaluating typhoid vaccine responses in specific antibody deficiency patients receiving immunoglobulin replacement.

Patients with specific antibody deficiency (SAD) have impaired immune function and suffer from recurrent infections. Some patients are treated with immunoglobulin replacement which involves receiving monthly infusions of pooled protective antibodies from healthy blood donors. This multi-centre study will be the first to investigate vaccine responses to a commonly used typhoid vaccine (Vi-polysaccharide; Vi-PS) in adult patients with SAD on immunoglobulin replacement. We hypothesise that Vi-PS vaccine responses will differ between SAD patients, in particular those who require long-term immunoglobulin replacement and those with less severe disease. This study will describe Vi-PS vaccine responses in SAD patients both on and off immunoglobulin replacement as well as healthy adults and patients with known antibody deficiency (common variable immunodeficiency). These groups will help us to understand normal and abnormal Vi-PS vaccine responses. Having more information on how to assess SAD patients on immunoglobulin replacement will help clinicians to better manage patients with SAD in the future.