Dose dependency of antibody response in infants and children to pneumococcal polysaccharides conjugated to tetanus toxoid

Three injections of tetravalent pneumococcal polysaccharide-tetanus toroid conjugate vaccine (PncT) were given to infants at 2, 4 and 6 months of age simultaneously with diphtheria-tetanus-pertussis and Haemophilus influenzae type b tetanus toroid conjugate vaccines. Three doses (1, 3 or 10 mu g) of polysaccharides were used. Children were boosted with unconjugated polysac charide vaccine at 14 months of age. No dose dependency was seen after prim ary immunization. however, booster response to three vaccine serotypes was highest in the group primed with the lowest dose of conjugate vaccine. As t he magnitude of the response to booster may be related to the number of pol ysaccharide-specific memory B cells, we hypothesize that the 10 mu g dose o f the tetravalent conjugate vaccine is too high for optimal induction of im munologic memory. (C) 1999 Elsevier Science Ltd. All rights reserved.