Article

Response to conjugate Haemophilus influenzae B vaccine among infants in Niamey, Niger

Centre de Recherche sur les Meningites et les Schistosomoses, Niamey, Niger.
The American journal of tropical medicine and hygiene (Impact Factor: 2.7). 11/1998; 59(5):837-42.
Source: PubMed

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.

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    • "In a RCT in Niger, infants given DTP at 6 weeks of age followed by HibV-TT at 10 and 14 weeks had greater anti-PRP antibody levels than infants given a three dose schedule of concomitant HibV-TT with DTP at 6, 10 and 14 weeks of age. The GMC following the first dose of HibV-TT administered at 10 weeks of age was (2.40 ␮g/ml), more than double and significantly higher than the GMC of the 6 weeks dose of HibV-TT [35]. Although some of the differences reported may reflect improved immune response in infants vaccinated at an older age, the more pronounced immune response may also reflect carrier priming with TT four weeks prior to the administration of HibV-TT. "
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