Pathogen and transmission
Haemophilus influenzae type B is a bacterium that, despite its name, has nothing to do with the influenza virus (flu pathogen). Seven different serotypes are known (serotypes a-f and non-typeable). Haemophilus influenzae lives in the nose and throat of many people, usually without it making them ill. However, it can also cause serious illness.
Human to human transmission takes place via droplet infection, e.g. through sneezing, speaking and coughing. Both healthy carriers and people with the disease can transfer Haemophilus influenzae.
Disease may occur if immune defences are not yet fully formed, or are reduced, for example in children under 5 years old, older people and other people with deficient immune systems.
Haemophilus influenzae can cause various illnesses, ranging from mild to serious. These include middle ear infections (otitis media), sinusitis, lung infections (pneumonia), inflammation of the epiglottis (epiglottitis), meningitis and blood infections (sepsis).
In infants and young children, Haemophilus influenzae type b is one of the most common causes of acute epiglottis infections (with risk of suffocation) and purulent meningitis. The disease can lead to permanent damage such as hearing loss or mental/physical disabilities, or even be fatal, despite the use of effective antibiotics.
Distribution and frequency
Haemophilus influenzae diseases occur around the world.
Before the introduction of the Haemophilus influenzae type b vaccine in 1990, approximately 200 severe cases of illness occurred per year in Switzerland, around 150 of which were in children aged under 5. Today, only around 10 children under 5 become ill, most of whom are not or only insufficiently vaccinated.
Infants must be vaccinated as early as possible to protect them from the disease. The vaccination against Haemophilus influenzae type b (a combined vaccination against diphtheria, tetanus, whooping cough, polio, hepatitis B and Haemophilus influenzae b) is recommended for all children at 2, 4 and 12 months. From 5 years of age, vaccination against Haemophilus influenzae is no longer necessary.