['To determine the function of capsular polysaccharide (CPS)-specific immunoglobulin-G (IgG) and neutrophils from older adults in increasing ingestion and killing of type V group B Streptococcus (GBS).', 'Cross-sectional study.', 'Outpatient clinic at Baylor College of Medicine.', 'The subjects were 40 healthy, community-dwelling adults aged 65 and older from Houston, Texas.', 'The serum level of type V GBS CPS-specific IgG was measured using an enzyme-linked immunosorbent assay. Functional activity was evaluated using an opsonophagocytosis assay.', 'Sera from four subjects promoted efficient neutrophil-mediated phagocytosis and killing of type V GBS (mean log10 reduction+/-standard deviation in colony-forming units (cfu)=1.51+/-0.39). Each had serum CPS-specific IgG concentrations exceeding 1 microg/mL. Sera from 36 subjects did not promote neutrophil-mediated functional activity (mean log10 reduction in cfu=-0.09+/-0.06; P=.025). Only one of these 36 had a CPS-specific IgG concentration exceeding 1 microg/mL. When pooled sera from young adults given type V GBS conjugate vaccine was added at CPS-specific IgG concentrations of 4 microg/mL or 0.4 microg/mL, sera from all subjects promoted neutrophil-mediated killing of type V GBS. No impairment was evident in the neutrophil function of elderly subjects when it was compared with that of young adults.'] Do healthy elderly people lack neutrophil-mediated functional activity to type V group B Streptococcus?