Can risk area designation help increase vaccination coverage for Tick-Borne Encephalitis? Evidence from German claims data

Abstract

Background and objectivesAlthough vaccine preventable, the incidence of tick-borne encephalitis (TBE) increased in Germany from 2001 to 2021 by on average 2% each year, with a peak of more than 700 TBE infections documented in 2020. TBE-risk areas, as designated by district based on incidence of human cases, expanded north- and northeastward, present in 11 of the 16 Federal States as of 2022. Using claims data from a German statutory health insurance in the Federal States of Saxony and Thuringia (AOK PLUS), we aimed to assess whether official assignment of a district to a risk area had an impact on vaccination rates in Germany. MethodsThe data covered the period from 01/01/2010 to 31/12/2018 and included information on vaccine administrations from outpatient physicians. Yearly incident vaccination rates were reported overall and by district. To investigate the association between a new designation of an incident TBE-risk area and vaccination rates, a difference-in-difference analysis was conducted. ResultsOverall, the incident vaccination rates increased from 6.2 to 9.5 per 1,000 person-years between 2012 and 2018, with a peak of 12.2 in 2015. While districts that had been risk-areas for the whole study period had always a higher vaccination rate compared to districts that were never categorized as risk areas, the increase between 2012 and 2018 was comparable in the two groups (3.0 and 3.2 per 1,000 person-years, respectively). In contrast, districts that were newly designated risk districts during the study period experienced a significantly larger increase in vaccination rates, going from 5.8 to 14.7 per 1,000 person-years between 2012 and 2018, with a peak of 19.6 in 2015. ConclusionThe results suggest that the new designation of a district as risk area has a significant positive impact on vaccination rates, which is strongest immediately after designation of risk area.