A randomized trial of conjugated group B streptococcal type Ia vaccine in a rabbit model of ascending infection

Am J Obstet Gynecol. 1999 Oct;181(4):803-8. doi: 10.1016/s0002-9378(99)70305-4.


Objective: Maternal vaccination may become a central strategy in the prevention of early-onset group B Streptococcal sepsis. Unlike earlier group B streptococcal polysaccharide vaccines that were poorly immunogenic, newer vaccines conjugated to tetanus toxoid have been developed and have improved immunogenicity. We sought to evaluate a conjugated vaccine using our rabbit model of ascending infection.

Study design: Rabbit does were randomized to receive either conjugated group B streptococcal type Ia (Ia-tetanus toxoid) or conjugated group B streptococcal type III (III-tetanus toxoid) vaccine. Does were vaccinated 7 days before conception and 7 and 21 days after conception. On days 28 to 30 of a 30-day gestation, does were inoculated intracervically with 10(6) colony-forming units of type Ia group B Streptococcus. Labor was induced if does were undelivered after 72 hours. Does were observed up to 7 days after inoculation. Offspring were observed up to 4 days. We obtained maternal cultures from the uterus, peritoneum, and blood and offspring cultures from the mouth, anus, and blood. Antibody levels were also determined.

Results: Offspring survival was significantly improved in the group receiving Ia-tetanus toxoid (P =.047). Outcomes such as maternal sepsis and severe illness, although not reaching statistical significance, showed a trend toward improved outcomes in the Ia-tetanus toxoid group.

Conclusions: This is the first study to evaluate the conjugated group B streptococcal vaccine by using any model of ascending infection. The Ia-tetanus toxoid vaccine led to improved survival and was immunogenic but fell short of its expected efficacy in preventing ascending group B streptococcal disease under these experimental conditions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Newborn / microbiology
  • Antibodies, Bacterial / blood
  • Bacteremia
  • Bacterial Vaccines* / immunology
  • Drug Evaluation, Preclinical
  • Female
  • Gestational Age
  • Immunoglobulin G / blood
  • Opsonin Proteins
  • Peritoneum / microbiology
  • Polysaccharides, Bacterial / immunology*
  • Pregnancy
  • Rabbits
  • Random Allocation
  • Streptococcal Infections / microbiology
  • Streptococcal Infections / prevention & control*
  • Streptococcus agalactiae / immunology*
  • Streptococcus agalactiae / isolation & purification
  • Tetanus Toxoid* / immunology
  • Uterus / microbiology
  • Vaccines, Conjugate / immunology


  • Antibodies, Bacterial
  • Bacterial Vaccines
  • Immunoglobulin G
  • Opsonin Proteins
  • Polysaccharides, Bacterial
  • Tetanus Toxoid
  • Vaccines, Conjugate
  • streptococcal polysaccharide Ia group B