Responses to the 23-valent pneumococcal polysaccharide vaccine will be measured by ELISA to determine the geometric mean increase in IgG antibody titer to pneumococcal polysaccharide (Pnc Ps) serotypes. Functional antibody, measured by percent kill of a known pneumococcal concentration, will be determined by opsonophagocytosis assay (OPA). Titers for serogroup 4 and serotypes 6B, 19F, and 23F will be measured, and geometric mean rises in antibody concentrations will be determined to measure response to vaccination.