Response to Special Emphasis Notice (NOT-HS-13-006) Problem: Despite great strides in improving immunization coverage in children, coverage falls far short of the Healthy People 2010 and 2020 goals. Yet, in recent years, the U.S. has experienced a re-emergence of many vaccine preventable diseases, making immunization coverage of great importance. In addition many children also receive unnecessary extra immunizations. Children who receive care from multiple providers or clinics, such as low-income children, are at greater risk for under and over immunization due to fragmented or incomplete immunization records. This proposal will evaluate the impact of implementing the proposed meaningful use (MU) Stage 3 objectives related to the exchange of immunization information from an Immunization Information System (IIS) to an electronic health record (EHR) system. While there are benefits to central reporting of immunization administrations to an IIS, as was included in the first two stages of the EHR MU incentive program, front line care providers are most likely to benefit when the IIS supplies them with immunization information at point of patient care directly in their EHR. In 2009, the New York Citywide Immunization Registry (CIR; New York City's IIS) implemented a system to allow clinical sites to download their patients' immunization records directly into their local EHRs. Since December 2009, Columbia University Medical Center has collaborated with the CIR to synchronize immunization data with its EHR. Thus, this collaboration between Columbia and CIR provides a unique position to demonstrate the efficacy of this proposed MU requirement involving immunization data exchange recommendations. Specific Aim 1: To assess the impact of immunization exchange from a regional IIS to a local EHR on under- and over-immunization of low-income, urban children and adolescents. Specific Aim 2: To assess the impact of immunization exchange from a regional IIS to a local EHR system on completeness of documentation of immunization status in the EHR. Methods: The records of approximately 15,000 children will be reviewed. We will assess under- and over- immunization in children with visits in a 6-month period prior to implementation of bidirectional exchange vs. a 6-month period post-implementation. We will also assess the impact of combining immunization records on completeness of documentation of immunization status in children with visits post-implementation of bidirectional exchange by comparing immunization status, with and without inclusion of IIS information. Outcome: The primary outcomes are under-immunization, over-immunization and completeness of documentation of immunization coverage (separately) according to the age specific CDC-recommended immunizations.