Tick-borne encephalitis (TBE), caused by the TBE virus (TBEV), is a serious public health threat in northern Eurasia. Three subtypes of TBEV are distinguished.
Inactivated vaccines are available for TBE prophylaxis, and their efficacy to prevent the disease has been demonstrated by years of implication. Nevertheless, rare TBE cases among the vaccinated have been registered. The present study aimed to evaluate the protective efficacy of 4 TBEV
vaccines against naturally circulating TBEV variants. For the first time, the protection was evaluated against an extended number of phylogenetically distinct TBEV strains isolated in different years in different territories. The protective effect did not strongly depend on the infectious dose of the challenge virus or the scheme of vaccination. All
vaccines induced
neutralizing antibodies in protective titers against the TBEV strains used, although the
vaccines varied in the spectra of induced
antibodies and protective efficacy. The protective efficacy of the
vaccines depended on the individual properties of the
vaccine strain and the challenge virus, rather than on the subtypes. The neutralization efficiency appeared to be dependent not only on the presence of
antibodies to particular
epitopes and the
amino acid composition of the virion surface but also on the intrinsic properties of the challenge virus E
protein structure.