ABSTRACT
The serotypes included in the currently licensed 7-valent pneumococcal conjugate vaccine (PCV7) were selected in part on the distribution of serotypes associated with invasive disease among U.S. children. Before the vaccine was introduced into the United States in 2000, the serotypes included in the vaccine caused approximately 80% of invasive infections in children younger than five years (10). On the basis of data available in 2000, the proportion of infections caused by 7valent serotypes is more than 50% in all regions of the world but with regional variation. Nevertheless, it appears that in some parts of Africa, Asia, and Europe, serotypes 1 and/or 5 account for a significant proportion of invasive infections in children, and thus are important for future vaccines (8).
