Comparison of self-report influenza vaccination coverage with data from a population based computerized vaccination registry and factors associated with discordance.

Objectives: We aim to compare influenza vaccination coverages obtained using two different methods; a population based computerized vaccination registry and self-reported influenza vaccination status as captured by a population survey.

Methods: The study was conducted in the Autonomous Community of Madrid (ACM), Spain, and refers to the 2011/12 influenza vaccination campaign. Information on influenza vaccination status according to a computerized registry was extracted from the SISPAL database and crossed with the electronic clinical records in primary care (ECRPC). Self-reported vaccine uptake was obtained from subjects living in the ACM included in the 2011-12 Spanish National Health Survey (SNHS). Independent study variables included: age, sex, immigrant status and the presence of high risk chronic conditions. Vaccination coverages were calculated according to study variables. Crude and adjusted prevalence ratios were computed to assess concordance.

Results: The study population included 5,245,238 adults living in the ACM in year 2011 with an individual ECRPC and 1449 adult living the ACM and interviewed in the SNHS from October 2011 to June 2012. The weighted vaccination coverage for the study population according to self-reported data was 19.77% and 15.04% from computerized registries resulting in a crude prevalence ratio (cPR) of 1.31 (95% CI 1.20-1.44) so self-reported data significantly overestimated 31% the registry coverage. Self-reported coverages are always higher than registry based coverages when the study population is stratified by the study variables. Self-reported overestimation was higher among men than women, younger age groups, immigrants and those without chronic conditions. Both methods provide the most concordant estimations for the target population of the influenza vaccine.

Conclusions: Self-report influenza vaccination uptake overestimates vaccination registries coverages. The validity of self-report seems to be negatively affected by socio-demographic variables and the absence of chronic conditions. Possible strategies must be considered and implemented to improve both coverage estimation methods.