INTRODUCTION

Streptococcus pneumoniae (the pneumococcus) remains no less important today as a pathogen of community-acquired pneumonia, meningitis, and acute otitis media than it has for the past several decades for several important reasons: (1) pneumococcal diseases, especially pneumococcal pneumonia, occur commonly; (2) invasive (bacteremic) pneumococcal diseases carry high case fatality rates; and (3) penicillin-resistant and multidrug-resistant strains continue to spread increasingly worldwide. Streptococcus pneumoniae ranks first as a cause of community-acquired pneumonia and second as a cause of bacterial meningitis and as an important bacterial pathogen of otitis media among infants and children. The high incidence and often fatal outcome of invasive disease despite prompt and appropriate antibiotic treatment provided the rationale for development and subsequent licensure in the United States of two effective polysaccharide vaccines, namely a 23-valent vaccine comprising 23 polysaccharides of the most common serotypes that are associated with community-acquired pneumonia in adults and children older than 2 years and a 7-valent conjugate vaccine comprising 7 polysaccharides, each conjugated to a carrier protein, of the 7 most common serotypes associated with community-acquired pneumonia and otitis media in infants and children younger than 2 years. The 7-valent conjugate vaccine is included now in the routine immunization program of all infants and children.

The emergence and continued frequent occurrence of penicillin resistant and multidrug-resistant strains underlie the urgency for the prevention of S. pneumoniae infection, especially in persons at high risk of serious disease.