title: Persistence of antibody at 18 months following vaccination of young Gambian infants with PRP-OMPC Haemophilus influenzae type b conjugate vaccine.
abstract: The rate of decline in anti-PRP antibody levels was measured in two groups of Gambian children who had been given PRP-OMPC at 1 and 3 months or 2 and 4 months of age. In the younger group (n = 70), the geometric mean titre fell from 1.32 micrograms/ml at 4 months to 0.44 micrograms/ml at 18 months. In the older group (n = 54), the geometric mean titre fell from 1.18 micrograms/ml at 5 months to 0.46 micrograms/ml at 18 months. The proportion of vaccinated children with antibody levels over 1.0 microgram/ml fell from 54% 1 month after the second dose of vaccine to 27% at the age of 18 months, while the proportion with levels over 0.15 micrograms/ml fell from 82% to 60%, with no significant differences observed between the vaccination groups. For those children who did not show evidence of environmental boosting, the half-life of anti-PRP antibody was about 100 days. This did not differ between the groups. These findings suggest that to provide lasting immunity PRP-OMPC should be given with a late booster dose at 12-15 months, as is the current practice in the USA. The need for a late booster dose may limit the value of this vaccine in developing countries where vaccination of children is difficult after the 1st year of life.
authors.affiliation: Medical Research Council Laboratories, The Gambia, West Africa.
authors.forename: E K
authors.initials: EK
authors.lastname: Mulholland
authors.forename: J
authors.initials: J
authors.lastname: Todd
authors.forename: M
authors.initials: M
authors.lastname: Rowe
authors.forename: H
authors.initials: H
authors.lastname: Campbell
authors.forename: P
authors.initials: P
authors.lastname: Byass
authors.forename: P P
authors.initials: PP
authors.lastname: Vella
authors.forename: V I
authors.initials: VI
authors.lastname: Ahonkhai
authors.forename: B M
authors.initials: BM
authors.lastname: Greenwood
mesh_terms: D000907:Antibodies, Bacterial / Q000096:biosynthesis*; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology*; D005500:Follow-Up Studies; D005714:Gambia; D018073:Haemophilus Vaccines; D006193:Haemophilus influenzae / Q000276:immunology*; D006801:Humans; D007223:Infant; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D014614:Vaccines, Synthetic / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001428:Bacterial Vaccines; D018073:Haemophilus Vaccines; C061964:Haemophilus influenzae-type b polysaccharide-Neisseria meningitidis outer membrane protein conjugate vaccine; D011135:Polysaccharides, Bacterial; D014614:Vaccines, Synthetic