The immunogenicity and safety of Haemophilus influenzae type b-tetanus toxoid conjugate vaccine in Gambian infants

SummaryIn developing countries, Haemophilus influenzae type b is a major cause of meningitis and pneumonia in the 1st year of life. The safety and immunogenicity of a Haemophilus influenzae type b polysaccharide-tetanus toxoid conjugate vaccine (PRP-T) were evaluated in two studies of Gambian infants. In the first study, 131 infants were recruited and randomized into three groups to receive PRP-T at 1 and 3 months (group A), PRP-T at 2 and 4 months (group B) or no PRP-T (group C). The liquid form of PRP-T was used. The geometric mean titre (GMT) of anti-PRP antibody 1 month after the second dose was 0.26 μg/ml in group A and 0.41 μg/ml in group B. In the second study, 66 infants were given PRP-T in the lyophilized form at 2, 3 and 4 months of age. The GMT 1 month after the first dose was 0.09 μg/ml, after the second 0.74 μg/ml and after the third 2.32 μg/ml. After the third dose, 72% of children had antibody levels greater than 1.0 μg/ml and 93% greater than 0.15 μg/ml. No serious side-effects were observ...