The frequency of CD4+/IFN-γ+ T cells directed to NS1 and NS5 and the frequencies of CD8+ /IFN-γ+ T cells to NS3 and NS5 were significantly higher in VBT cases than in unvaccinated TBE cases, confirming the results obtained in the IFN-γ ELISpot assay (Fig. 4A and Supplementary Fig. 3). Here, CD4 is linked to tick-borne encephalitis.