 The diagnostic performance of Typhim Vi response and allohemagglutinins will be analyzed by calculating sensitivity, specificity, predictive values, likelihood ratios and Receiver Operating Characteristic curves for Typhim Vi and allohemagglutinins using pneumococcal antibody response as the reference standard. The association between low Typhim Vi response or low allohemagglutinins and clinical signs of polysaccharide antibody deficiency will be studied by multiple logistic regression. 