Haemophilus influenzae meningitis 5 years after introduction of the Haemophilus influenzae type b conjugate vaccine in Brazil

Abstract

The long-term impact of Haemophilus influenzae type b (Hib) conjugate vaccine, introduced throughout Latin America in the late 1990s, has not been evaluated. Active surveillance for H. influenzae meningitis was performed from August 9, 1996 to August 8, 2004 in Metropolitan Salvador, Brazil. Five years after the introduction of Hib conjugate vaccine, Hib meningitis incidence decreased from 2.39 to 0.06 cases per 100,000 population (98%) overall, and from 60.9 to 3.1 cases per 100,000 population (95%) in children <1 year of age. A transient serotype replacement phenomenon was observed associated with a small increase of meningitis due to two H. influenzae type a clonal groups. These findings indicate that Hib immunization campaign has led to the virtual elimination of Hib disease in this region.

Impact ofHaemophilus influenzaetype b vaccination on the incidence of invasiveHaemophilus influenzaedisease in France, 15 years after its introduction

“…This conclusion differs from initial studies performed in Portugal and Brazil after the introduction of routine vaccination [27,28]. However, replacement of type b strains by type a in Brazil was shown to be a local and transient phenomenon which did not reach a level sufficiently large to call into question the Hib conjugate vaccination policy [14]. Similarly, the increase in the number of non-encapsulated isolates in Portugal was also transient [25].…”

Epidemiology ofHaemophilus influenzaeSerotype a, North American Arctic, 2000–2005

“…Ribeiro et al noted an 8-fold increase in the incidence of Hia meningitis from the prevaccine (0.02 per 100,000 population) to postvaccine period (0.16 per 100,000 population) in Brazil (32). However, more recently published data by this group demonstrate that the increase in incidence during the year following vaccine introduction was not observed in subsequent years (33). A study by Millar et al has demonstrated high rates of invasive Hia disease among Navajo and White Mountain Apache children in the southwestern United States, although no increase in Hia incidence was noted after the introduction of Hib vaccine (10).…”

Developing a vaccine for Haemophilus influenzae serotype a: Proceedings of a workshop

“…Five years after the introduction of the Hib conjugate vaccine, the overall incidence of Hib meningitis in the general population had decreased from 2.39 to 0.06 per 100,000. However, transient serotype replacement by two clones of Hia was observed (9). The changing epidemiology of invasive H. influenzae disease globally requires further study.…”