Vaccines to Protect Older Adults against Pneumococcal Disease.

Determining the optimal vaccination strategy for the protection of the elderly population against pneumococcal disease remains a challenge. Older adults are, second to young infants, most susceptible to become colonized and invaded by Streptococcus pneumoniae, causing serious disease such as bacteremic pneumonia, sepsis, and meningitis. In an era with increasing antimicrobial resistance and the growing susceptible population of aged adults, S. pneumoniae is a priority bacterial pathogen for research and development of new intervention strategies. While elderly indirectly profit from infant immunization programs through herd immunity, vaccination of older age groups can offer more direct protection. Two types of pneumococcal vaccines for adults, both based on capsular polysaccharide serotypes, are currently available but have limitations, such as short-lived protection or limited serotype coverage. These vaccine limitations and the biological aging of the immune system call for novel vaccination strategies for the older adults. Here, we highlight how host-pathogen interactions, immune protection, and effectiveness of currently available vaccines shift with increasing age, and how future pneumococcal vaccine strategies could be tailored for the elderly.