Antibody response of Mexican infants to Haemophilus influenzae type b capsular polyribosylribitol phosphate. Differences between natural and vaccine induced (Oligosaccharide-CRM197 conjugated vaccine) immunization

In this study we compared natural vs induced Haemophilus influenzae type b (hib) anti-capsular polyribosylribitol phosphate (PRP) antibody response in a low socioeconomic population. One hundred twenty five 2-month-old children received the complete HbOC vaccine immunization scheme and a boster dose at 15 month of age. One hundred twenty five non-immunized children served as the control group. Serum Hib anti-PRP antibody titers were determuined by ELISA in all children. We found at the end of the primary immunization scheme an antibody concentration of 27.28 µg/ml in the immunized group vs. 7.48 µg/ml in the control group. The antibody response was mainly of the IgG1 class in both groups. After the booster dose the antibody concentration was 30.14 g/ml in the vaccinated group vs. 6.06 µg/ml in the control group (p<0.01). Ninety nine percent of immunized and non-immunized infants had titers greater than 1 µg/ml. These results confirm that immunization with the HbOC vaccine induces an important increase in anti-PRP specific antibody titer, but they also demonstrate that natural exposure induces responses higher than those referred as protective (1 µg/ml)

Effect of different concentrations of diphtheria toxoid & aluminum phosphate on potency of diphtheria component in DPT vaccines.

An effort was made to determine the optimum concentration of diphtheria toxoid in combination with aluminum phosphate gel in DPT vaccines which may give a safe, potent and economical preparation. The effect of four different concentrations of aluminum phosphate and three different antigenic concentrations of diphtheria toxoid on potency of diphtheria component in DPT vaccine was assessed. A gradual increase in potency was seen with increase in toxoid concentration and a gradual decrease in potency with the increase in aluminum phosphate content. Vaccines made with minimum quantities of toxoid (30 Lf/ml) and aluminum phosphate (3 mg/ml) were found to be highly satisfactory. Vaccines prepared with high antigenic purity toxoid have better potency, as compared to those prepared with a relatively low antigenic purity toxoid.