MAGNITUDE, DURATION, QUALITY, AND FUNCTION OF PNEUMOCOCCAL VACCINE RESPONSES IN ELDERLY ADULTS

The suboptimal efficacy of the currently available 23-valent pneumococ cal vaccine in the growing population of adults >65 years old may be r elated to the limited immunogenicity of the vaccine polysaccharides in this group. In this study, the majority of elderly outpatients with s table chronic illnesses generated a vigorous IgG response to seven vac cine serotypes comparable to that of healthy young adults at 1, 3, and 16 months after immunization. Moreover, the quality and function of a nticapsular antibodies, measured as avidity and in vitro opsonization, were comparable between elderly and young subjects over time. However , a subset (similar to 20%) of elderly outpatients responded to fewer than two of seven serotypes tested 1 and 3 months after immunization, whereas none of the healthy young adults were such poor responders. Th us, despite the adequate mean immune responses of the elderly as a gro up, a substantial proportion of elderly persons may have poor response s to the currently available pneumococcal vaccine.