What is the primary capsular serotype responsible for the majority of Haemophilus influenzae infections?

The primary capsular serotype responsible for the majority of Haemophilus influenzae infections is type b (Hib). This particular serotype is important because it is associated with invasive diseases such as meningitis and epiglottitis, particularly in children. The presence of the polysaccharide capsule in serotype b enhances its virulence, allowing it to evade the host's immune response more effectively than other serotypes. Vaccination against Hib has significantly reduced the incidence of diseases caused by this bacterium in vaccinated populations, highlighting the importance of this serotype in public health. Other serotypes of Haemophilus influenzae, although they can cause disease, are less commonly associated with severe infections compared to type b.