title: Response to conjugate Haemophilus influenzae B vaccine among infants in Niamey, Niger.
abstract: Despite near elimination of Haemophilus influenzae b (Hib) meningitis from several industrialized countries following introduction of conjugate Hib vaccines into infant immunization schedules, Hib remains a major cause of meningitis and pneumonia in resource-poor countries. In Niger, Hib causes nearly 200 cases of meningitis per 100,000 children < one year of age, and > 40% of cases are fatal. We evaluated the immunogenicity of Hib polysaccharide-tetanus toxoid conjugate vaccine (PRP-T) administered in the same syringe as diphtheria-tetanus-pertussis (DTP) vaccine among infants in Niger. Infants were randomized into group 1 (PRP-T at six, 10, and 14 weeks), group 2 (PRP-T at 10 and 14 weeks), or a control group (meningococcal A/C polysaccharide vaccine). By 14 weeks of age, all subjects in groups land 2 had > or = 0.15 microg/ml of anti-PRP antibody, and 82% versus 76% had > or = 1.0 microg/ml of antibody (P=not significant). By nine months of age the proportion of infants with > or = 0.15 and > or = 1.0 microg/ml was group I=97% and 76%; group 2=93% and 67%; controls=10% and 2.6%. Four weeks after the first, second, and third doses of PRP-T, infants in group 1 showed geometric mean titers (GMTs) of 0.19, 3.97, and 6.09 microg/ml while infants in group 2 had GMTs of 2.40 and 4.41 microg/ml four weeks after the delayed first and second doses. Both PRP-T groups had significantly higher GMTs at 18 weeks and nine months of age than infants in the control group. The Hib PRP-T vaccine was immunogenic in infants in Niger. The strong response after PRP-T was initiated one month after the first DTP vaccination may reflect carrier priming. Two dose schedules of PRP-T should be given serious consideration, particularly if their reduced cost permits vaccine introduction that would be otherwise unaffordable.
authors.affiliation: Centre de Recherche sur les Meningites et les Schistosomoses, Niamey, Niger.
authors.forename: G
authors.initials: G
authors.lastname: Campagne
authors.forename: A
authors.initials: A
authors.lastname: Garba
authors.forename: A
authors.initials: A
authors.lastname: Schuchat
authors.forename: D
authors.initials: D
authors.lastname: Boulanger
authors.forename: B D
authors.initials: BD
authors.lastname: Plikaytis
authors.forename: M
authors.initials: M
authors.lastname: Ousseini
authors.forename: J P
authors.initials: JP
authors.lastname: Chippaux
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D003365:Costs and Cost Analysis; D018073:Haemophilus Vaccines / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D007231:Infant, Newborn; D008583:Meningitis, Haemophilus / Q000276:immunology / Q000517:prevention & control; D009548:Niger; D013745:Tetanus Toxoid / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology
chemical_list: D000907:Antibodies, Bacterial; D018073:Haemophilus Vaccines; C055753:Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate; D013745:Tetanus Toxoid; D018074:Vaccines, Conjugate