Abstract
Background Underimmunization against influenza has been increasing in
recent years. A spatial clustering of underimmunization is suspected. These
clusters can pose risks to health care and make achieving immunization
quality standards difficult. The objectives of this paper are to (a)
identify and describe PLZ-level spatial clusters with high levels of
underimmunization against influenza, (b) compare the clusters with other
preventive services, and (c) model possible factors influencing
underimmunization.
Material and methods From the routine data of the Association of
Statutory Health Insurance physicians Westphalia-Lippe, patients ≥60
years and vaccinations between 2012–2017 were extracted. As a
methodology, the spatial scan statistics were chosen, which show high
relative risks of underimmunization in clusters.
Results and conclusion Four statistically significant clusters of
underimmunization against influenza were identified, which proved to be
stable even after adjustment with the temporal trend of local
underimmunization rates. In the flu season 2016/2017, the
underimmunization rate in the higher risk clusters (RR>1) was
71.9–74.7% and the rate outside these clusters was
67.0%. As influencing factors on underimmunization, socio-economic
factors and vaccination behavior in the preseason were identified.
Underimmunization rates are geographically clustered. The spatial scan
statistics can be used for the identification of persistent clusters in
order to carry out targeted spatial and addressee-specific measures to
reduce underimmunization rates.
Key words
Influenza - Vaccination - Underimmunization - spatial Cluster - Secondary Data Analysis
