Haemophilus influenzae type b vaccination: long-term protection.

OBJECTIVE To identify evidence of the impact of Haemophilus influenzae type b (Hib) conjugate vaccine on the epidemiology of invasive Hib disease. SOURCES OF DATA This review was based on a search of MEDLINE, LILACS, technical reports, national and international guidelines (publications from 1991 to 2005). The keywords Haemophilus influenzae type b, immunization, impact, and effectiveness, alone or in combination, were used to retrieve the articles. Studies published before 1991 and cited in the references of the studies reviewed were analyzed for useful information. SUMMARY OF THE FINDINGS Introduction of the Hib conjugate vaccine produced great decline in the incidence of invasive Hib disease in childhood in countries where this vaccine was introduced into the routine immunization schedule. Nevertheless, the resurgence of invasive Hib disease in some regions has challenged several researchers to identify the reasons for this epidemiological pattern, as well as the measures to be implemented in order to avoid such a phenomenon. CONCLUSIONS The use of Hib conjugate vaccine on a population scale has been greatly effective; nonetheless, changes in the vaccination scheme seem to be necessary to keep invasive Hib disease under control.