In the 50 states and 6 cities that operate registries regionally or state-wide, an average of 36% of private provider sites submitted data to the immunization information systems (IIS) during the last six months of 2003. Arkansas, Connecticut, the District of Columbia, Mississippi, and South Dakota reported over 95% of their private immunization provider sites submitting data to the IIS. The results are based on self reported data from CDC immunization grantees.

MA and MD provider participations are not reported. Within each state, only Boston and Baltimore City reported rates. The rates were too small to reflect a more accurate picture of provider participation in each state.

Qualifier: reported annual fluctuations in private provider participation may be due to programmatic and/or technical changes to the immunization information system.