Streptococcus pneumoniae is one of the leading bacterial pathogens causing invasive disease and non-invasive infections at both extremes of life: in children younger than 5 years and in elderly persons of 65 years or more. Pneumococcal infections result in substantial morbidity and mortality among children under 5 years of age; it is estimated that 1,600,000 deaths occur per year in that age range alone, mostly in developing countries, thus representing a serious public health problem around the globe. Infections caused by S. pneumoniae are considered by the World Health Organization (WHO) as the number one vaccine-preventable cause of death in children younger than 5 years of age. In 2000, the first heptavalent conjugated pneumococcal vaccine (PCV7) was licensed in the United States, differing from the already available non-conjugated polysaccharide pneumococcal vaccine in its ability to induce a protective immune response in children under 2 years of age. Initial efficacy studies in the United States with PCV7 revealed a 97.4% efficacy against invasive pneumococcal disease (IPD) caused by vaccine serotypes (4, 9V, 14, 19F, 23F, 18C and 6B). PCV7 was introduced into the National Immunization Program (NIP) of various countries starting in year 2000 and, after 11 years of use, the data confirm that PCV7 introduction resulted in a major reduction of S. pneumoniae IPD, non-bacteremic pneumonia, otitis media medical visits, the need for tympanic tubes, the number of cases of otorrhea and of various antimicrobial resistant strains in children <5 years of age. Additionally, reductions in S. pneumoniae infections have been observed in unvaccinated children above 5 years of age and adults including individuals older than 65 years of age (herd effect). Effectiveness has been observed in countries using a 4-dose regimen (3 infant doses followed by a booster during the second year of life) but also in countries with modified reduced doses (2 infant doses and a booster during the second year of life or after 3 infant doses with no booster).
