Euringer et al.
Tick-borne encephalitis virus IgG antibody surveillance: vaccination- and infection-induced seroprevalences, south-western Germany, 2021
Euro Surveill. 2023;28(12):2200408. doi:10.2807/1560-7917.ES.2023.28.12.2200408

The exact epidemiology of TBE virus infections is unknown in Germany. Measuring antibodies directed against the glycoprotein E cannot distinguish between vaccine- and naturally induced antibodies. However, by use of an ELISA specific for the non-structural protein 1 (NS-1), one can identify individuals who have produced antibodies after an infection by the virus rather than after vaccination, because NS-1 is not included in whole virion TBE vaccines, and thus vaccinees remain TBE virus NS-1 negative but infected individuals become NS-1 positive (see Snapshot week 26/2021, Snapshot week 9/2020, Newsletter April 2020).

A seroprevalence study with overall 2,220 blood samples has been carried out in southwestern Germany (Federal state of Baden-Württemberg, Ortenau district), in which a NS-1 IgG ELISA was used in combination with a (glycoprotein E) TBE ELISA in order to test the TBE IgG prevalence in blood donors and to evaluate the proportion of TBE virus infected and vaccinated persons.

57% of the blood samples tested positive using the screening of TBE virus IgG ELISA. All samples tested either positive or borderline (n=1,369) were subsequently tested in a NS-1 ELISA, of which 125 tested positive indicating a NS-1 seroprevalence of 5.6% in the study population.

It was calculated that the yearly average incidence based on the NS-1-ELISA was 283 (mostly asymptomatic) infections per 100,000 inhabitants in the investigated region. This surveillance study revealed that the real incidence by far exceeds the number of notified TBE cases (4.7/100,000).

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