Geographic variation in invasive pneumococcal disease following pneumococcal conjugate vaccine introduction in the United States.

Background: Rates of invasive pneumococcal disease (IPD) varied among the United States before pneumococcal conjugate vaccine (PCV7) introduction. We compared trends in IPD rates among diverse US sites over 10 years since PCV7 introduction.

Methods: Patients with IPD of all ages were identified through active population and laboratory-based surveillance in 8 geographic areas under continuous surveillance during 1998-2009.