The highest incidence rates of IPD occur in children less than five years old and adults 60 years and older; those at highest risk for infection with Streptococcus pneu- moniae.

Invasive pneumococcal disease (IPD) is caused by the bacteria Streptococcus pneumoniae. It is spread through having close contact with someone who has the bacteria in their nose and mouth, including asymptomatic carriers. IPD occurs when the pneumococcal bacterium invades a normally sterile site and can cause pneumonia, sepsis (blood poisoning) and meningitis.