Incidence of Haemophilus influenzae type b meningitis during 18 years of vaccine use: observational study using routine hospital data

摘要

Despite the spectacular success of Haemophilus influen-zae type b (Hib) conjugate vaccines in the developed world, failures have become more common in the Netherlands and the United Kingdom, where the incidence of invasive Hib diseases at age 0-4 years per 100 000 increased from 0.66 in 1998 to 2.96 in 2001. An immunological defect is not to blame. This increase in failure coincided with the change from whole cell pertussis to combined three component acellular vaccine (DTaP-Hib). This combination lowers Hib antibodies. The clinical significance is unclear. Acellular vaccine cannot be blamed in the Netherlands, where whole cell vaccine was still used. Both countries have been giving Hib vaccination at age 2, 3, and 4 months; a booster at 11 months is given in the Netherlands. Another characteristic in the United Kingdom is concomitant meningococcal group C conjugate. Replacement of serotypes other than Hib in severe diseases has also raised concern. Because H influenzae meningitis in the Greater Helsinki area has been recorded since 1939, we had a unique opportunity to investigate any impact of vaccination.