Comparing a computer-based childhood vaccination registry with parental vaccination cards: a population-based study of Delaware children.

We conducted a population-based study in Delaware to examine the reliability of childhood vaccination data in a comprehensive computer-based record system versus parental vaccination cards. We sampled 1,005 children born between January, 1991, and September, 1993. We oversampled for children whose mothers received Medicaid or were uninsured at the time of delivery. Of the survey responders, 276 (56%) had access to written records, and 409 (83%) records were located in the Delaware immunization computer database. The kappa coefficient was 0.18. The observed agreement was 59.8%. When the two databases were combined, the up-to-date rate for 2-year-olds was 58.4%, an increase of 12.7% and 24.2% from the computer database and the parental records, respectively. The computer database was 78.1% sensitive and the parental records were 54.9% sensitive. These results indicate that a comprehensive computer-based record system, with adequate provider participation and proper data management, can be more reliable than parental vaccination cards.