Haemophilus influenzae is a bacteria which exists in many forms. The type B form called HIB, commonly produces diseas in human by colonizing the upper respiratory tract of up to 80% of the population and is major cause of infection and mortality in children.

Almost all HIB disease occurs in children younger than 5years, and mostly in children younger than 1 year.

Transmission of HIB from one individual to another primarily occurs via respiratory secretions from carriers. however, HIB can also be spread through direct contact with a person with HIB disease but this is relatively uncommon accounting for only 2% of cases in children younger than 4 years old.

The manifestation of HIB disease are varied with the most serious being meningitis and epiglottitis (Inflammation of the lid covering the organs for breathing).