An immunization information system (IIS) is a confidential, computerized, population-based system that collects and consolidates vaccination data from vaccine providers and provides tools for designing and sustaining effective immunization strategies at the provider and program levels. Among the capabilities of an IIS are the capacity to inform vaccine providers of upcoming patient vaccination needs; generate vaccination coverage reports, patient reminders, or recalls for past due vaccinations; and interoperate with electronic health record (EHR) systems. In 2010, the Task Force on Community Preventive Services recommended that immunization information systems be used to increase vaccination coverage after showing strong evidence of their effectiveness. A Healthy People 2020 objective is to increase to 95% the percentage of children aged <6 years whose immunization records are housed in a fully operational IIS. To assess IIS progress toward meeting the Healthy People objective, CDC analyzed data from the 2009 Immunization Information Systems Annual Report (IISAR) survey (completed by 53 of 56 federal grantees with IIS sites), which indicated that 77% of all U.S. children aged <6 years participated in an IIS, an increase from 75% in 2008. In addition, 59% of grantees reported being able to send and receive vaccination data using Health Level Seven (HL7) messaging standards, and 73% reported that some vaccine providers with EHR systems in their geographic area were providing vaccination data directly to an IIS from EHRs. Enhancing IIS and EHR with standards such as HL7 will provide greater consistency in data exchange and likely help to improve the quality and timeliness of IIS data.