SAFETY AND IMMUNOGENICITY OF TETRAVALENT PNEUMOCOCCAL VACCINES CONTAINING 6B, 14, 19F AND 23F POLYSACCHARIDES CONJUGATED TO EITHER TETANUS TOXOID OR DIPHTHERIA TOXOID IN YOUNG INFANTS AND THEIR BOOSTERABILITY BY NATIVE POLYSACCHARIDE ANTIGENS

Background. New vaccines against pneumococcal infections in infancy ar e needed, We assessed in young infants the safety and immunogenicity o f two tetravalent vaccines containing pneumococcal 6B, 14, 19F and 23F polysaccharides conjugated to either tetanus toroid (Pnc-T) or diphth eria toroid (Pnc-D), Methods, Pnc-T or Pnc-D containing 3 mu g of poly saccharide of each of the four pneumococcal polysaccharides or placebo were given intramuscularly in a double blinded fashion (25 infants pe r group) at 2, 4 and 6 months of age, At 12 months of age all 75 child ren were boosted with a 23-valent nonconjugate polysaccharide pneumoco ccal vaccine, Serum type-specific anticapsular antibody concentrations were measured at 2, 4, 6, 7, 12 and 13 months of age, Adverse events occurring within 72 h after each injection were recorded, Results, Bot h Pnc-T and Pnc-D were well-tolerated, Pnc-T and Pnc-D had higher anti body concentrations compared with placebo after primary immunity (type 6B, 1.66, 1.40 and 0.60 mu g/ml, respectively; type 14, 4.81, 2.65 an d 2.22 mu g/ml, respectively; type 19F, 2.40, 3.48 and 0.83 mu g/ml,re spectively; type 23F, 0.96, 0.44 and 0.35 mu g/ml, respectively). Prop ortions of infants with concentrations above 1.0 mu g/ml were also hig her in the vaccine recipients than in those given placebo. After boost er with the nonconjugate polysaccharide vaccine, both geometric antibo dy concentration and proportion with concentrations greater than or eq ual to 1.0 mu g/ml were significantly higher among either Pnc-T or Pnc -D recipients than among placebo recipients. Conclusions. Both Pnc-T a nd Pnc-D were well-tolerated, induced serotype-specific anticapsular a ntibodies and induced immunologic memory.