The pneumococcal polysaccharide vaccine (PPSV) is designed to protect against infections caused by the Streptococcus pneumoniae bacteria. This vaccine helps the immune system recognize and fight off these bacteria, which can lead to serious illnesses like pneumonia, meningitis, and bloodstream infections. PPSV is recommended for certain groups, including older adults and individuals with specific health conditions. It is administered as a single injection and is effective in preventing many types of pneumococcal disease. However, it does not provide protection against all strains of the bacteria, so additional vaccines may be recommended for comprehensive protection.