About 10,000 instances of tick-borne encephalitis (TBE), a severe central nervous system disease caused by TTEV, are documented world-wide every year. Approximately 30,000 cases are documented worldwide. The most important measure of illness prevention continues to be vaccination with TBE.  Healthy adults aged 18-60 were twice vaccinated at 30-d intervals to examine the safety and immunogenicity of Evervac. In TBE endemic areas the study had been monoblind, randomised, comparative, controlled and carried out. A comparative treatment was employed with the commercial lyophilized vaccine TBE-Moscow. The incidence, intensity and duration of adverse events were observed by the individuals. The seriousness of local and systemic reactions was reported to be low to severe in the Evervac vaccination group. In both seronegative and seropositive recipients, immunisation with Evervac has led to a considerable growth in the geometric mean titer (GMT) of anti-TBEV antibodies.

For the originally seronegative receivers, the seroconversion rate after the first dosage was 69% and after the second dosage was 100%. There were no major differences among the study and the vaccination control groups in these parameters. Thus, Evervac, an adjuvant-free vaccine based on Vero, exhibited a good tolerance, low reactogenicity and a marked immune reaction and in general was not inferior to the commercial adjuvant TBE vaccine.

Reference: https://www.tandfonline.com/doi/full/10.1080/21645515.2020.1757990