Voluntarily Reported Immunization Registry Data: Reliability and Feasibility to Predict Immunization Rates, San Diego, California, 2013
OBJECTIVES: Accurate data on immunization coverage levels are essential to public health program planning. Reliability of coverage estimates derived from immunization information systems (IISs) in states where immunization reporting by medical providers is not mandated by the state may be compromised by low rates of participation. To overcome this problem, data on coverage rates are often acquired through random-digit-dial telephone surveys, which require substantial time and resources. This project tested both the reliability of voluntarily reported IIS data and the feasibility of using these data to estimate regional immunization rates. METHODS: We matched telephone survey records for 553 patients aged 19-35 months obtained in 2013 to 430 records in the San Diego County IIS. We assessed concordance between survey data and IIS data using κ to measure the degree of nonrandom agreement. We used multivariable logistic regression models to investigate differences among demographic variables between the 2 data sets. These models were used to construct weights that enabled us to predict immunization rates in areas where reporting is not mandated. RESULTS: We found moderate agreement between the telephone survey and the IIS for the diphtheria, tetanus, and acellular pertussis (κ = 0.49), pneumococcal conjugate (κ = 0.49), and Haemophilus influenzae type b (κ = 0.46) vaccines; fair agreement for the varicella (κ = 0.39), polio (κ = 0.39), and measles, mumps, and rubella (κ = 0.35) vaccines; and slight agreement for the hepatitis B vaccine (κ = 0.17). CONCLUSIONS: Consistency in factors predicting immunization coverage levels in a telephone survey and IIS data confirmed the feasibility of using voluntarily reported IIS data to assess immunization rates in children aged 19-35 months.