Immunization information systems (IIS) are confidential, computerized, population-based systems that collect and consolidate vaccination data from vaccination providers and provide important tools for designing and sustaining effective immunization strategies at the provider and immunization program levels. These tools include clinical decision support, vaccination coverage reports, interoperability with electronic health record systems, vaccine inventory management, and the ability to generate reminder and recall messages. In 2010, based on strong evidence of effectiveness, the Task Force on Community Preventive Services recommended IIS use as a means of increasing vaccination rates. A Healthy People 2020 target (IID-18) is to increase to 95% the proportion of children aged <6 years whose immunization records are in fully operational, population-based IIS. To monitor progress toward program goals, CDC annually surveys 56 immunization program grantees (50 states, five cities, and the District of Columbia) using the IIS Annual Report (IISAR). Results from the 2010 IISAR (completed by 54 grantees) indicate that 82% (18.8 million) of U.S. children aged <6 years participated in IIS, as defined by having at least two recorded vaccinations, an increase from 78% (18.0 million) in 2009. Among 52 grantees who responded to questions about the Vaccine Tracking System (VTrckS), CDC's new national vaccine ordering and inventory management system for publicly purchased vaccine, 38 (73%) indicated their intention to use the IIS in their state or city to interface with VTrckS. Use of IIS to interface with VTrckS might provide additional incentive for vaccination providers to participate in IIS and enhance IIS utility by supporting efficient and effective methods for providers to order vaccine and track inventory and by promoting greater accountability of publicly purchased vaccine.