Impact of conjugate pneumococcal vaccines on the changing epidemiology of pneumococcal infections.

Streptococcus pneumoniae-related infections have a major global impact on healthcare, especially in the developing world, and are considered the number one vaccine-preventable cause of death in children. There are more than 90 pneumococcal serotypes and 46 serogroups. The first capsular polysaccharide pneumococcal vaccine was licensed in the USA in 1977 for individuals older than 2 years of age at high risk for pneumococcal disease. Two decades later, the first 7-valent pneumococcal polysaccharide-protein conjugate vaccine completed the required clinical trials and was introduced as part of the national immunization program of various countries. New-generation vaccines that include emerging serotypes, while maintaining protection against the 7-valent pneumococcal serotypes, have recently been approved. With the addition of these serotypes, the majority of potential pneumococcal serotypes causing invasive disease in most parts of the world could be covered.