A Phase 2, Randomized, Control Trial of Group B Streptococcus (GBS) Type III Capsular Polysaccharide-tetanus Toxoid (GBS III-TT) Vaccine to Prevent Vaginal Colonization With GBS III

Clin Infect Dis. 2019 May 30;68(12):2079-2086. doi: 10.1093/cid/ciy838.


Background: Group B Streptococcus (GBS) frequently colonizes pregnant women and can cause sepsis and meningitis in young infants. If colonization was prevented through maternal immunization, a reduction in perinatal GBS disease might be possible. A GBS type III capsular polysaccharide (CPS)-tetanus toxoid conjugate (III-TT) vaccine was evaluated for safety and efficacy in preventing acquisition of GBS colonization.

Methods: Healthy, nonpregnant women aged 18-40 years and screened to be GBS III vaginal and rectal culture negative were randomized to receive III-TT conjugate or tetanus diphtheria toxoid vaccine in a multicenter, observer-blinded trial. GBS vaginal and rectal cultures and blood were obtained bimonthly over 18 months. Serum concentrations of GBS III CPS-specific antibodies were determined using enzyme-linked immunosorbent assay.

Results: Among 1525 women screened, 650 were eligible for the intent-to-treat analysis. For time to first acquisition of vaginal GBS III, vaccine efficacy was 36% (95% confidence interval [CI], 1%-58%; P = .044), and for first rectal acquisition efficacy was 43% (95% CI, 11% to 63%; P = .014). Two months post-immunization, geometric mean concentrations of serum GBS type III CPS-specific immunoglobulin G were 12.6 µg/mL (95% CI, 9.95 to 15.81) in GBS III-TT recipients, representing a 4-fold increase from baseline in 95% of women, which persisted. Both vaccines were well tolerated.

Conclusions: GBS CPS III-TT conjugate vaccine significantly delayed acquisition of vaginal and rectal GBS III colonization. In addition to its use for maternal immunization to passively protect infants with maternally derived antibodies, a multivalent vaccine might also serve to reduce fetal and neonatal exposure to GBS.

Clinical trials registration: NCT00128219.

Keywords: GBS; rectal colonization; vaccine; vaginal colonization.

Publication types

  • Clinical Trial, Phase II
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Antibodies, Bacterial / blood
  • Antibodies, Bacterial / immunology
  • Bacterial Capsules / immunology*
  • Female
  • Humans
  • Immunogenicity, Vaccine
  • Immunoglobulin G / blood
  • Immunoglobulin G / immunology
  • Outcome Assessment, Health Care
  • Streptococcal Infections / prevention & control*
  • Streptococcal Vaccines / administration & dosage
  • Streptococcal Vaccines / immunology*
  • Streptococcus agalactiae / classification
  • Streptococcus agalactiae / immunology
  • Vaccination
  • Vaccines, Conjugate / immunology
  • Vaginosis, Bacterial / prevention & control*
  • Young Adult


  • Antibodies, Bacterial
  • Immunoglobulin G
  • Streptococcal Vaccines
  • Vaccines, Conjugate
  • group B streptococcal type III capsular polysaccharide-tetanus toxoid vaccine

Associated data

  • ClinicalTrials.gov/NCT00128219