Older adults disproportionately sustain morbidity and mortality due to vaccine-preventable illnesses. Despite this observation, adult immunization rates continue to lag behind national goals. Reduced vaccine efficacy in older adults leading to apathy regarding the need for vaccine administration, unrealistic expectations for disease prevention rather than reduced illness severity, and system issues that make vaccine administration and tracking difficult all contribute to this problem. In this review, the biologic and system-based causes for vaccine failure in aged adults are reviewed, issues of efficacy and cost-effectiveness in older adults are summarized for influenza and pneumococcal vaccine, and ways to improve vaccine effectiveness in older adults, now and in the future, are outlined.