Advances in Pneumococcal Vaccines

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Streptococcus pneumoniae causes considerable morbidity and mortality in the elderly. There are three established approaches to pneumococcal vaccination: polysaccharide vaccines, protein-polysaccharide conjugate vaccines and protein-based vaccines. This article reviews advances in anti-pneumococcal vaccines, with reference to advantages and shortcomings for the elderly in particular. The 23-valent polysaccharide pneumococcal vaccine (PPV) is currently recommended for high-risk patients and the general elderly population. Although the effectiveness of PPV against pneumonia is unclear, recent studies point to significant protective effects in preventing pneumococcal pneumonia and reducing the severity of disease in vaccinated elderly patients. PPV offers high serotype coverage and, although it is poorly immunogenic in some individuals, provides approximately 60% protection against invasive disease in the general elderly population. PPV vaccination appears cost effective for elderly patients although the vaccine might only be effective in preventing invasive disease. Additional benefits could mean a greater level of vaccine cost effectiveness. However, it is important to understand that PPV provides incomplete protection, especially in those with underlying high-risk conditions, and development of more effective pneumococcal vaccination strategies for elderly patients is still needed. In recent years, the most important advance in the prevention of pneumococcal infections in the elderly has been the introduction of a 7-valent conjugate pneumococcal vaccine (CPV) as a routine vaccination for infants. In addition to dramatically reducing invasive infection in children, CPV has been observed to have a considerable indirect protective effect in parents and grandparents. While the possibility of using CPV in elderly patients has been suggested, currently there are only limited immunogenicity data and no efficacy data in adults. The low serotype coverage is an important shortcoming and if CPV were to be used in the elderly, it would need to be given sequentially with the PPV. New CPVs covering more serotypes are currently under investigation, and these could be an alternative for use in all groups in the future. Numerous protein-based vaccine candidates offer the potential advantage of prevention against infections caused by all pneumococcal serotypes. Several are in various stages of development in animal models, but none can be expected to be available in clinical practice for several years at least. To date, the 23-valent PPV is still the best anti-pneumococcal vaccine option in the management of elderly persons. Introduction of the 7-valent CPV as a routine vaccine for children has provided considerable indirect benefits for older adults via herd immunity, but this vaccine has limited serotype coverage in elderly individuals. New CPVs including more serotypes (various CPVs are in different phases of pre-licensure studies) could prove to be good options in the future for all age groups. Several protein-based pneumococcal vaccine candidates (currently under investigation in animal models) offer the potential advantage of serotype independent protection, but none can be expected to be available in clinical practice in the near future.