Résumé : A new generation of vaccines against Haemophilus influenzae type b (Hib) has been developed at the end of the last decade. These vaccines are based on the principle of capsular polysaccharide coupled with a protein antigen, confering the characteristics of a T-dependant antigen to the entire molecule : antibody response after the first months of life and induction of an immune memory. Prospective studies revealed the protective nature of the vaccine. In most European and North American countries, where vaccination has been generalised for toddlers, the invasive infections caused by H. influenzae b have been reduced by 95% in less than 5 years after its introduction. In these countries, vaccination also showed to decrease the nasopharyngeal portage. In Belgium the first conjugated anti-Hib vaccine was made available at the beginning of 1993. Immunisation coverage studies made in 1996 revealed that vaccination was not generalised, since the cost of vaccination was left to the parents. A study performed by the "Groupement Belge des Pédiatres Francophones" (G.B.P.F.) within the pediatric services of the French Community, revealed a progressive decrease of the number of invasive infections with Hib, though this decrease was less important than observed in the countries where vaccination had been generalised. These results were confirmed by the evolution of the number of isolates sent to the reference laboratory.