In 2007, 71% of the U.S. children less than 6 years of age participated in a grantee immunization information system (IIS). Twelve states and three cities reported over 95% of their children greater than 4 months and less than 6 years of age with at least two immunizations in the IIS. Fourteen states and the District of Columbia were approaching the national health objective, with participation of 81%-94%.

Qualifier: reported annual fluctuations in child participation may be due to programmatic and/or technical changes to the immunization information system. The denominator used to calculate child participation numbers are drawn from the 2007 Census for each state and city.