The risk of invasive Streptococcus pneumoniae infection (primarily bacteraemia and meningitis) is greatest among the very young and the very old. Persons in certain racial groups, including African-Americans, American Indians, Native Alaskans and Australian Aborigines, are also at increased risk of disease. Other factors that appear to increase the risk of pneumococcal infection are lower socioeconomic status, recent infection with influenza and possibly other viral respiratory tract infections, chronic medical conditions, and immunosuppressive medications. Reported annual incidences of invasive pneumococcal disease among persons aged > or = 65 years in North America and Europe range from 25 to 90 cases/100,000 persons. In the US and Canada, these rates represent between 15,000 and 30,000 cases annually among the elderly. Mortality caused by pneumococcal infections is highest among the elderly, with nearly 1 in 5 cases resulting in death. Worldwide, S. pneumoniae is the leading cause of community-acquired pneumonia requiring hospitalisation. The high fatality rates, as well as recent outbreaks of pneumococcal infection among unvaccinated nursing home residents and the emergence of drug-resistant pneumococcal strains, highlight the importance of preventing invasive infection by vaccination.