Invasive Haemophilus influenzae disease: epidemiology and clinical spectrum before large-scale H. influenzae type b vaccination.

In a prospective study between January 1987 and December 1992, 103 patients with invasive Haemophilus influenzae (Hi) infection were identified in a well-defined population before large-scale Haemophilus influenzae type b (Hib) vaccination was introduced. The incidence (case/100,000/year) of invasive Hi infection was 5.9 for the whole population, 55 for children 0-4 years old and as high as 2.8 for adults. Hib was the predominant cause of the infection (83 cases) in children but, in adults, 13/39 (30%) cases were caused by non-typable Hi and 6/39 (19%) by Hi serotype f. Three patients (3%) died and 6 (5.8%) suffered a permanent sequel from the infection. All patients with such a sequel had invasive Hib infection. No significant difference between patients 0-6 years old and matched controls regarding the frequency of subnormal serum levels of immunoglobulins was found.