FIG. 3.

CFU of bacteria versus dilution of serum samples (A and B) or delta OD versus dilution of serum samples (C and D) for serotype 6B (A and C) and serotype 19F (B and D). One sample is a serum pool, Ppool10 (solid square), and the others are serum samples from three persons who received a pneumococcal PS vaccine 1 month prior to phlebotomy. Delta OD was expressed in milliabsorbance units and was obtained by subtracting the OD₄₅₀ obtained at the beginning of the color development from the OD₄₅₀ after 2 h of color development.