Comparing potential benefits of new pneumococcal vaccines with the current polysaccharide vaccine in the elderly.

We compared the hypothetical effects of the 23-valent polysaccharide pneumococcal vaccine with new vaccines on preventing invasive and noninvasive pneumococcal disease in persons >or=65 years. We estimated how much disease would occur if no polysaccharide vaccine were in use and used this baseline to compare the polysaccharide, a 7-valent conjugate vaccine, and hypothetical common antigen vaccine. The polysaccharide, conjugate, and common antigen vaccines prevented 10.6, 10.7, and 17.7% of invasive disease and 4.3, 5.6, and 10.0% of pneumonia, respectively. Superior effectiveness of new vaccines was dependent upon a presumed longer duration of protection than the 23V-PPV and effectiveness against noninvasive pneumonia. Our results suggest that new vaccines could improve disease prevention.