FIG. 2.

Effect of increasing ammonium SCN concentration in the serum diluting buffer on serum antibody binding to meningococcal C polysaccharide in an ELISA. The serum pools were diluted to an antibody concentration yielding an OD of approximately 1 in the absence of SCN. Pool A289 was prepared from sera of adults vaccinated with meningococcal polysaccharide vaccine. Toddler pools 1 and 2 were prepared from postvaccination sera of toddlers given meningococcal polysaccharide vaccine or meningococcal C conjugate vaccine. All subjects showed greater-than-fourfold increases in concentrations of IgG anticapsular antibody in response to vaccination. Toddler pool 1 included postvaccination sera with bactericidal antibody (BCA) titers of ≥1:8, whereas toddler pool 2 contained postvaccination sera with bactericidal antibody titers of <1:8 (presumed to have lower antibody avidity).