How effective is pneumococcal polysaccharide vaccine at preventing pneumococcal carriage or disease?

According to CDC, more than 80% of healthy adults who receive PPSV23 develop antibodies against the serotypes contained in the vaccine that persist for at least 5 years. Older adults and people with some chronic illnesses or immunodeficiency may not respond as well and their antibody levels may decline more quickly.

Overall, the vaccine is 60% to 70% effective in preventing invasive pneumococcal disease caused by serotypes in the vaccine. PPSV23 shows less effectiveness among immunocompromised people; however, because of their increased risk of invasive pneumococcal disease, CDC recommends PPSV23 for people in these groups who receive PCV15. There has not been consensus regarding the ability of PPSV23 to prevent non-bacteremic pneumococcal pneumonia; however, recent observational studies reported 21%–46% effectiveness against PPSV23-type pneumococcal pneumonia when PPSV23 was given less than 5 years before illness onset.

Unlike conjugate vaccines, PPSV23 vaccination has not been shown to decrease nasal carriage of pneumococcal bacteria among those vaccinated.