The 23-valent pneumococcal polysaccharide vaccine (PPSV23) has been recommended for prevention of invasive pneumococcal disease (IPD) in adults since 1983.
1 Most studies show that PPSV23 provides some protection against IPD, but studies have reached contradictory conclusions about its ability to prevent nonbacteremic pneumococcal pneumonia (NPP),
1,2 which causes several hundred thousand illnesses annually in the United States.
3