Elderly individuals are at an increased risk for serious pneumococcal infection. The efficacy of the licensed pneumococcal vaccine is also lower in this at risk population. The precise immunologic reason for the increased susceptibility and decreased efficacy with advancing age is unknown. Understanding and improving the response to pneumococcal vaccine in persons over the age of 65 is an important step in preventing this serious illness. The proposed study will evaluate the relative safety and immunogenicity of 9-valent CRM 197 protein-conjugated pneumococcal polysaccharide (CRM-PS) compared to the currently licensed 23-polysaccharide (PS) vaccines in elderly adults. In addition, the response to revaccination following conjugate vaccine will also be evaluated. Outcome measurements will include adverse effects, standard ELISA measurements of serotype specific antibody, as well as antibody response to carrier protein, effects on functional antibody status and on nasal carriage of S. pneumoniae. The study will be conducted in 180 adults who are 65 years of age and older and who have not received pneumococcal vaccine within the last 5 years. Patients will be assigned to 1 of 3 groups at random in a double blind manner. One dose of vaccine and 1 dose of placebo or 2 doses of 9-valent CRM-PS vaccine will be administered at an interval of 4 months and compared to a single dose of PS vaccine and 1 dose of placebo. Subjects will be evaluated for local and system side effects using a 7-day diary card and clinical and telephone follow-up. Serologic evaluation will be done before and 1 month following each vaccination or placebo. Subjects who received CRM-PS will receive a dose of PS vaccine 8 months after the first dose of vaccine, and potential priming by previous conjugate vaccine will be assessed by measuring the quality and quantity of the antibody response to revaccination. Participants will be involved in study related procedures for up to 268 days.