Impact of anti-Hib conjugate vaccine on the incidence of Haemophilus influenzae meningitis in Brazil's Federal District: results of a three-year follow-up]

INTRODUCTION: Type b Haemophilus influenzae (Hib) continues to be an important causative agent of various infectious processes, and its encapsulated strains cause invasive disease. In some aboriginal populations, the incidence of Hib infections in children under five is greater than 400 per 100,000. In the seventies and eighties, vaccines against Hib were developed after antibodies against the capsular component were identified. The objective of this paper was to estimate the impact that the vaccine against Hib has had in Brazil's Federal District since it was introduced in March of 1998. METHODS: Using population-based data obtained from Brazil's Federal District's Ministry of Health's Surveillance System, rates of incidence of meningitis during the three years that preceded and that followed the introduction of the anti-Hib vaccine were compared. Comparisons were also drawn between changes in the trends observed. RESULTS: A comparison of the data from the two periods showed a decrease of approximately 90% in the incidence of Hib meningitis, but no concomitant decrease in other forms of bacterial meningitis was noted. There was also a proportional increase in the number of cases among infants 6 months of age and under due to a drop in the incidence of the disease in children older than 6 months. CONCLUSION: As a result of the introduction of the conjugated anti-Hib vaccine in Brazil's Federal District, the incidence of Hib meningitis among children 7 months to 35 months of age dropped from 168 per 100,000 to 15 per 100,000 (91.1%).