Marvik et al.
Low prevalence of tick-borne encephalitis virus antibodies in Norwegian blood donors.
Infect Dis. 2020, in press, doi: 10.1080/23744235.2020.1819561
The first TBE case in Norway was reported in 1998. Since then, Norway is considered a low-endemic TBE country. Ixodes ricinus is distributed along the coast as far as the Arctic Circle, but only parts of the southern coast region are endemic for TBE.
Recently, a seroprevalence study has been carried out from February 2019 to March 2020 in 1136 blood donors of 18-70 years of age and living in Vestfold and Telemark county in southern Norway. After the first TBE virus IgG ELISA analysis, 93.9% of the donors were concluded TBE IgG negative. 58 reactive samples were then analyzed by neutralization assay. 21 of the IgG ELISA positive samples were NT positive, while all borderline ELISA samples were NT negative.
Of the 21 NT positive blood donors, 17 reported a previous TBE vaccination. Thus, only 0.4% of the enrolled blood donors had NT antibodies without previous vaccination. Cross-reactions in the ELISA were seen in blood donors who had previous vaccination with other flavivirus vaccinations. Regarding TBE awareness, half of the blood donors were familiar with TBE, but only 35% knew about a TBE vaccine.