This vaccination, which is actually called the pneumococcal vaccine, can prevent serious infections called pneumococcal diseases. These life-threatening diseases include pneumonia, meningitis and septicemia.
www.webmd.com/vaccines/pneumococcal-vaccine-schedule
PNEUMONIA
Pneumonia is an infection that causes air sacs in the lungs to fill with fluid or pus, making it difficult to breathe. While some cases of pneumonia are relatively mild, it can be a life-threatening illness, particularly among those over 65, children, and those with weakened immune systems.
http://www.mayoclinic.org/diseases-conditions/pneumonia/home/ovc-20204676
MENINGITIS
Meningitis causes inflammation of the membranes that protect the brain and spinal cord. This inflammation is often caused by an infection—either bacterial or viral— that invades the fluid that surrounds the spinal cord and brain. However, it is also possible to get meningitis from a physical injury, a parasite, or fungal spores. While the prognosis may vary depending upon the health of the patient at the time of infection, meningitis can be life-threatening.
www.cdc.gov/meningitis/index.html
SEPTICEMIA
Septicemia (also called blood poisoning) is caused by an overwhelming immune system response to an infection. The chemicals the body uses to fight infection trigger inflammation, which can damage internal organs and cause blood clots. In the most severe cases, it can cause vital organs to fail. Septicemia is a serious illness that progresses quickly.
www.webmd.com/a-to-z-guides/sepsis-septicemia-blood-infection