Dobler et al.
Serological protection rates against TBEV infection in blood donors from a highly endemic region in southern Germany
Vaccines. 2023;11(3):522. doi:10.3390/vaccines11030522

In Germany, the TBE vaccination rate is not easy to calculate and is based on various data: annual vaccination certificates of schools’ starting pupils, statistics retrieved from health care insurers, and self-reporting from the vaccine manufacturers. In the federal state of Baden-Wuerttemberg, located in southern Germany, the vaccination rate lies at about 25% with wide ranges between the districts. This vaccination rate, assessed by the Robert Koch-Institut is based on the TBE vaccination recommendations, that means three injections as primary immunization and regular boosters after three or five years. In contrast to the vaccination rate, the seroprotection rate is based on the presence of neutralizing antibodies and is independent from recommended (and undertaken) vaccination schedules.

So far, no systematic study has been carried out to measure the TBE seroprevalence / TBE protection status in Germany. This has now been done in the Ortenaukreis district in Baden-Wuerttemberg (for which the vaccination rate was reported below 30% by the RKI) by analyzing blood samples from more than 2000 blood donors.

When blood samples were analyzed by TBE-IgG ELISA, 57% (1257/2220) were positive. Nearly all these sera tested positive in a neutralization assay (98%, 1244/1257) with a good correlation between OD values and NT titers, showing that the TBE-IgG ELISA might be a suitable epidemiological tool to indicate serological protection against TBE and confirm vaccine protection to a high degree in regions where TBE virus is the only flavivirus circulating and patients did mostly not receive other flavivirus vaccines.

The higher seroprotection rates compared to vaccination rates indicate that the duration of protection conferred by vaccination may be reassessed, also after an incomplete or irregular vaccination scheme and/or non-regular or missed booster vaccinations. The presented results may indicate a longer persistence of TBE vaccination-induced antibody titers than previously estimated.

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