SAFETY AND IMMUNOGENICITY OF A CONJUGATED HAEMOPHILUS-INFLUENZAE TYPE-B POLYSACCHARIDE-NEISSERIA MENINGITIDIS OUTER-MEMBRANE PROTEIN VACCINE

This study was performed to determine the immunogenicity and safety of a conjugate Haemophilus influenzae type b (Hib) vaccine (PedvaxHIB(R) ; Merck Sharp & Dohme Inc, West Point, PA, USA) in Taiwanese children. There were two groups in this study. Group A included 56 infants at 2 months of age, who received an initial dose of Hib conjugate vaccine at age 2 months and 4 months. Another booster dose was given between 1 2 and 15 months of age. Group B included 58 children, aged 11 to 14 mo nths, who were vaccinated at the time of enrollment and 2 months after the first vaccination. The results showed that this Hib conjugate vac cine was highly immunogenic with 100% and 86% of vaccinees in group A developing anti-Hib polyribosylribitol phosphate (PRP) antibody titers above 0.15 mu g/mL and 1 mu g/mL, respectively, after two vaccination s. A slightly better response rate was observed in group B, with 100% and 97% of vaccinees developing antibody titers above 0.15 mu g/mL and 1 mu g/mL, respectively, after two vaccinations. A significant booste r effect was seen in group A; the proportion of subjects with antibody titers above 1 mu g/mL increased fr om 38% to 95%, and the geometric mean titer increased from 0.68 to 11.92 mu g/mL. Adverse reactions wer e uncommon. Mild reactions consisted of low-grade fever and local disc omfort. We conclude that the Hib conjugate vaccine is highly immunogen ic and safe when given to Taiwanese children as young as 2 months of a ge.