THE ANTIBODY-RESPONSE TO SECONDARY IMMUNIZATION WITH PNEUMOCOCCAL POLYSACCHARIDES IN MICE

The benefit of re-immunization with pneumococcal polysaccharide vaccin e is an important question in clinical practice. In an experimental mo del, BALB/c and CBA/J mice were re-immunized s.c. with a 23-valent pne umococcal polysaccharide vaccine at various time intervals after a fir st immunization with the same vaccine. The antibody response after the secondary immunization showed similar kinetics as after primary immun ization, and was mainly an IgM antibody response. Re-immunization at 2 8 days or earlier induced a decrease in the serum antibody levels to t he vaccine. Reimmunization at 120 days or later induced higher antibod y levels than after the first immunization. Significant increases in a ntibody levels to serotypes 1, 4, 7F and 19F out of six serotypes test ed were observed. In CBA/J mice, but not in BALB/c mice, the dose used for primary immunization appeared to influence the magnitude of the a ntibody response to secondary immunization. Our results indicate that the time interval between primary and secondary immunization is an imp ortant determinant with regard to the magnitude of the antibody respon se to re-immunization with pneumococcal polysaccharide vaccine.