What is the MOST common cause of bacterial meningitis in children under five years of age?

The most common cause of bacterial meningitis in children under five years of age is Haemophilus influenzae type B (Hib). Historically, before the widespread use of the Hib vaccine, Hib was the leading cause of bacterial meningitis in this age group. The bacterium is a significant pathogen in young children and can lead to severe complications if not treated promptly.

The introduction of the Hib vaccine in the 1990s significantly reduced the incidence of meningitis caused by this organism. However, it remains crucial to recognize Hib as a primary cause for bacterial meningitis, given the populations that may not have full vaccination coverage. This context highlights the importance of vaccination programs in preventing infections that can have lasting effects on young children's health.

While other bacteria listed can also cause meningitis, Hib has been particularly notorious in this age group due to its prevalence prior to the vaccination era, making it a critical focus in both public health initiatives and clinical awareness.