Use of type V group B streptococcal conjugate vaccine in adults 65-85 years old.

One-third of the cases of invasive group B streptococcal (GBS) disease now occur in adults >or=65 years old. Serotype V is most frequent among these invasive isolates. The safety and immunogenicity of type V GBS capsular polysaccharide (CPS)-tetanus toxoid (V-TT) conjugate vaccine (CV) were assessed in 32 healthy adults 65-85 years old who were randomized to receive a single intramuscular dose of V-TT CV (n=22) or licensed tetanus-diphtheria toxoid vaccine (Td) (n=10; double-masked design). V-TT CV elicited significant increases in type V CPS-specific immunoglobulin (Ig) G, IgM, and IgA serum concentrations 4, 8, 26, and 52 weeks after immunization. V-TT-induced type V CPS-specific antibodies promoted the opsonophagocytic killing of type V GBS in vitro. Both vaccines elicited similar concentrations of TT-specific IgG in 4-week postimmunization serum samples. These results suggest the potential for prevention of invasive type V GBS infections in healthy elderly adults through immunization.