Streptococcus Pneumonia: Herd Effects and Emergence of Potentially Virulent Serotypes PCV13_Impact of NP Colonization, Herd Effects and Emergence of Potentially Virulent Serotypes of Pneumococci

The specific aim is to evaluate the impact of PCV13 as administered in the pediatric primary care clinic at Boston medical center on the serotype specific carriage of Streptococcus pneumoniae in children < 5.

Specifically the investigators will measure the decline in vaccine serotypes, the proportion of children receiving vaccine required to achieve 50% reduction in serotype specific carriage and the correlation between immunogenicity of the specific serotypes and decline in carriage. The study has been extended to complete 5 years of surveillance to determine the new SP serotype distribution at the time presumably a new equilibrium has been achieved.