Immune responses of infants vaccinated with serotype 6B pneumococcal polysaccharide conjugated with tetanus toxoid

Pediatr Infect Dis J. 1997 Jul;16(7):667-74. doi: 10.1097/00006454-199707000-00009.


Background: Streptococcus pneumoniae is a major cause of meningitis, bacteremia, pneumonia and otitis media. Pneumococcal polysaccharides are not immunogenic in infants, but improved immunogenicity of polysaccharide-protein conjugates has been demonstrated. Antibiotic-resistant pneumococci have increased the need for an effective vaccine.

Objective: To study the safety and immunogenicity of a pneumococcal type 6B polysaccharidetetanus toxoid conjugate (Pn6B-TT) in infants and to assess the function of antibodies.

Methods: Healthy infants were injected, Group A at 3, 4 and 6 months (n = 21) and Group B at 7 and 9 months (n = 19). Booster injection was given at 18 months. Antibodies were measured by enzyme-linked immunosorbent assay and radioimmunoassay, and functional activity was measured by opsonization of radiolabeled pneumococci. Nasopharyngeal cultures were obtained.

Results: No significant adverse reactions were observed. Pn6B-IgG (enzyme-linked immunosorbent assay) increased to a geometric mean of 0.62 microgram/ml (P = 0.367, compared with prevaccination titers) in Group A at 7 months and 1.22 micrograms/ml (P < 0.001) in Group B at 10 months. Total Pn6B antibodies (radioimmunoassay) were 44 ng of antibody N/ml (P < 0.053) in Group A and 211 ng of antibody N/ml (P < 0.001) in Group B. A smaller increase in IgM and IgA anti-Pn6B was observed. Reinjection at 18 months elicited booster responses in total and IgG anti-Pn6B; 62% of those in Group A and 79% of those in Group B had > 300 ng of antibody N/ml. Opsonic activity, after initial and booster vaccinations, correlated with Pn6B-antibody titers. Three infants with nasopharyngeal cultures repeatedly positive for serogroup 6 had poor serum IgG responses.

Conclusion: Our results demonstrate that Pn6B-TT is safe, elicits functional antibodies and memory responses in infants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Bacterial / blood
  • Antibodies, Bacterial / immunology
  • Female
  • Humans
  • Immunoglobulin A, Secretory / analysis
  • Infant
  • Male
  • Nasopharynx / microbiology
  • Phagocytosis
  • Polysaccharides, Bacterial / adverse effects
  • Polysaccharides, Bacterial / immunology*
  • Saliva / immunology
  • Streptococcus pneumoniae / isolation & purification
  • Tetanus Toxoid / adverse effects
  • Tetanus Toxoid / immunology*
  • Vaccination
  • Vaccines, Conjugate / immunology


  • Antibodies, Bacterial
  • Immunoglobulin A, Secretory
  • Polysaccharides, Bacterial
  • Tetanus Toxoid
  • Vaccines, Conjugate
  • streptococcal polysaccharide-tetanus toxoid conjugate vaccine