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Streptococcus pneumoniae gram stain

Pneumococcal Disease

What is it?

Pneumococcal disease is caused by the bacterium Streptococcus pneumoniae. This disease can cause a variety of symptoms ranging from ear infections to pneumonia to meningitis, which is inflammation of the lining of the brain and spinal cord. 
Infants should get 4 doses of the pneumococcal vaccine (PCV13) at 2 months, 4 months, 6 months, and 12 through 15 months.

PCV13 is very effective: It prevents approximately 96% of pneumococcal disease caused by vaccine serotypes. In the first three years that the vaccine was used, it prevented more than 3000 deaths.

What's the difference between them?

These vaccines all protect against pneumococcal disease. The number in each name refers to the number of serotypes that the vaccine protects against (PCV13 protects against 13 serotypes). PCV stands for Pneumococcal Conjugate Vaccine. PPSV stands for Pneumococcal Polysaccharide Vaccine. 

The CDC recommends PCV13 for all children younger than 2 years old (as part of the recommended schedule) and people 2 through 18 years old with certain medical conditions.


For those who have never received any pneumococcal conjugate vaccine, CDC recommends PCV15 or PCV20 for adults 65 years or older and adults 19 through 64 years old with certain medical conditions or risk factors. If PCV15 is used, this should be followed by a dose of PPSV23.


CDC also recommends PPSV23 for children 2 through 18 years old with certain medical conditions.

Relevant Terms

  • Antibody: a protein made by the immune system in response to a foreign particle (antigen). These proteins circulate in the blood and help defend the body against the substance.  

  • Antigen: This is any substance that triggers the immune system to create antibodies. For example, allergens such as pollen are antigens. 

  • Bacteria: A type of single-celled organism. Some can cause disease, but many are harmless and some actually benefit humans by living in the intestines and helping with digestion 

  • Bacterium: The singular of bacteria (one bacterium, two bacteria)

  • Conjugate: Attaching an antigen to a protein in order to improve the protection the vaccine provides. 

  • Meningitis: inflammation of the lining of the brain and spinal cord. 

  • Pneumonia: an infection in the lungs that causes air sacs to fill with fluid

  • Polysaccharide: another word for sugar. Polysaccharide vaccines use sugars as antigens.

  • Serotype: a group of strains within a species that share a particular type of surface structure. 

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