As its name would imply, streptococcus pneumoniae causes pneumonia, typically as a secondary complication of a viral infection like influenza or measles. However, this is no one-trick pony. Pnemococcus can also cause meningitis, sepsis, and less serious infections like sinusitis and otitis media (the common childhood ear infection). World-wide, it is responsible for more serious bacterial infections than any other bacteria. There are dozens of strains of S. pne out there and we cannot vaccinate for all of them, but we’ve got the most serious ones covered. There are many different versions of the pneumococcus vaccine as different strains tend to cause the most trouble in different age groups and risk populations. For example, individuals with sickle cell disease are more susceptible to pneumococcal infections because they don’t have a functioning spleen, which would usually protect them from encapsulated organisms like pneumococcus. Thus, we give these patients a 23-strain version of the vaccine. Your average healthy infant gets the 13-strain version. Adults get a totally different version. Since the introduction of the vaccine, nations that use it have seen a dramatic decrease in cases of pneumococcal disease but also in overall infant mortality. Neat, huh?