Comparative evaluation of conjugate vaccines in the Haemophilus influenzaeinfection model

We used a murine model of Haemophilus influenzae type b (Hib) infection to analyze the immunologic response to two commercially available PRP conjugat e vaccines (HbOC, PRP-T). The mortality rate in mice infected with a large dose of the bacteria after vaccination with HbOC or PRP-T at two and three doses was significantly lower than in non-vaccinated mice and mice vaccinat ed by one dose. Furthermore, for infections caused by a small bacterial dos e, the mortality rate in mice vaccinated with one, two, or three doses was significantly lower than in non-vaccinated mice. The induction level of ant i-PRP antibodies, especially IgG, in serum of mice vaccinated by two or thr ee doses was higher than in those vaccinated with a single dose. Our result s indicate that the dose of vaccine influences its efficacy in protecting a gainst Hib infection. Our results also showed a lack of difference between two different PRP conjugate vaccines.