This project will examine the safety and serological response to a currently licensed Merck vaccine, lypholized Pedvax HIB 15 mcg to a liquid 7.5 mcg Pedvax HIB; the advantage of the newer vaccine is lower dose and liquid formulation which is the first necessary step to a combined DPT/HIB vaccine. The investigator component of this research is to examine the effect of the two vaccines on nasopharyngeal carriage of H. influenzae type b in young children.