Abstract
In 2005, the Colorado Department of Public Health and Environment audited a sample of kindergarten school records to determine vaccination coverage at school entry. In addition to the audit, the traditional method of collecting immunization data by self-reports from schools continued through that school year. The results of the two surveys were compared. The audit results indicated that 76.3% (n = 1,776; 95% confidence interval 73.2, 79.4) of Colorado's kindergarteners received all required vaccines. In contrast, the series coverage estimated from school self-reports for the same time frame was 89.4% (n = 46,559). Self-reports by school staff in Colorado appear to overestimate the immunization status of children entering kindergarten. Because more than three-quarters of U.S. states use some form of school self-report to assess immunization status, this finding has significant implications for most state health departments.