<qa>  What is the main cause of morbidity and mortality?Pneumococcus is a major cause of morbidity and mortality. In 2000, a pneumococcal conjugate vaccine PCV was licensed for use in children and is now part of the routine childhood vaccine schedule. PCV is known to reduce invasive disease and protect against nasopharyngeal NP acquisition of vaccine serotype pneumococci; it also results in an increased risk of nonvaccine serotype carriage. This study proposes to assess the longterm impact of vaccine on NP carriage in a setting where there is intense antibody pressure on the ecology of the pneumococcus. A cross sectional study of pneumococcal NP colonization among American Indian children will be combined with surveillance for invasive disease in the same population. The purpose is to determine the impact of community wide PCV use on NP colonization and the relationship with invasive disease. This longterm safety issue needs to be assessed to fully evaluate the impact of vaccine on NP ecology and invasive disease. 