What is the epidemiological impact of Haemophilus influenzae?

Before the widespread use of the Hib vaccine, Haemophilus influenzae type b was a leading cause of bacterial meningitis and other invasive diseases in children under 5 years. The incidence of invasive Hib disease has dramatically decreased in countries with high vaccination coverage. However, non-encapsulated strains and other serotypes continue to cause significant morbidity and mortality, particularly in older adults and immunocompromised individuals.