Haemophilus influenzae: Vaccine Preventable Diseases Surveillance Standards

Overview

The bacteria Haemophilus influenzae type b (Hib) was the leading cause of non-epidemic bacterial meningitis worldwide in children prior to the introduction of Hib vaccine. H. influenzae can be unencapsulated or capsulated (six capsular types or serotypes), although 95% of severe disease is caused by capsular type b (Hib). H. influenzae can asymptomatically colonize the human nasopharynx, particularly in children.

The bacteria can spread contiguously to cause otitis media and sinusitis or be aspirated to cause pneumonia. More rarely, it can cause invasive disease, predominantly meningitis and pneumonia but also epiglottitis, septic arthritis and others. Over 90% of invasive H. influenzae disease occurs in children < 5 years of age, the majority in infants; children in less developed settings tend to be infected earlier in infancy. Case fatality rates can be high for H. influenzae meningitis, ranging from 5% with proper treatment to as high as 60% without. Among survivors, 20-40% suffer sequelae such as deafness and blindness. It is estimated that in 2008, 199 000 HIV-negative children < 5 years of age died from H. influenzae disease (1). HIV-infected infants are at a several-fold increased risk of invasive H. influenzae disease.