Impact of immunization against Haemophilus influenzae on the incidence of invasive Haemophilus influenzae infections in the Nord-Pas-de-Calais area.

Background. - In industrialized countries where immunization against Haemop hilus influenzae b (Hib) is largely used, the incidence of invasive Hib inf ections has dramatically decreased. The aim of this study was to analyse th e impact of immunization against Hib on the incidence of invasive Hib infec tions in the Nord-Pas-de-Calais area in France. Patients and methods. - This retrospective multicenter stud enrolled 11 of the 18 hospitals in the Nord-Pas-De-Calais area, comparing two periods: 199 1-1993 (before immunization), and 1994-1996 (during immunization). All chil dren less than 60 months of age and having an invasive Hib infection were i ncluded. The Pasteur-Merieux Company was asked to provide the number of vac cines sold in the Nord-Pas-de-Calais area during the study period. Results. - The number of vaccines sold in 1992 was 56,208; this reached 189 ,173 in 1996, corresponding to an immunization ratio higher than 90%. One h undred and two children representing 155 invasive Hib infections were studi ed. The annual incidence was 42 during the first period (meningitis: 18.6; septicemia; 14.6; epiglottitis; 5.6), and nine (meningitis: 5; septicemia: 2.6; epiglottitis: 0.3) during the second period, that is a 78% decrease. Conclusion. - These results confirm previous data in the literature by demo nstrating that immunization in the Nord-Pas-de-Calais area has dramatically decreased the incidence of invasive Hib infections. (C) 1999 Elsevier, Par is.