The Condition of Post-Vaccination Immunity to the Tick-Borne Encephalitis Virus in the Population Highly Endemic Area with Siberian Subtype Domination

Relevance. Modern inactivated culture vaccines against tick-borne encephalitis (TBE) with at least 70% of the population living in the  natural foci of the FE give a high epidemiological effect. Unresolved  issues are the simplification of the cumbersome vaccination scheme,  the optimal number of revaccinations, the protective titer of  antibodies against the Siberian subtype of the TBE virus dominant in Russia.

Goal of this work is to study the state of postvaccinal immunity in the population of the highly endemic area of the Trans-Urals.

Materials and methods. 1381 blood serum of the population vaccinated from 3 to 13 times with vaccines was studied: unconcentrated culture inactivated from strain No. 205 of the TBE  virus produced by «Virion», Tomsk, «EnceVir» produced by  «Microgen», Tomsk, produced by Chumakov Federal Scientific Center for Research and Development of Immuneand-Biological Products of  Russian.To identify specific antibodies – IgG, IgM, antigen of TBE  virus, sets of reagents of ELISA from «Vector-Best» were used.  Neutralizing activity of sera was determined by the index of  neutralization index with 4 strains of the Siberian subtype of TBE  virus.

Results. The immune layer among the vaccinated population in 10 districts of the Kurgan region, which differ in epidemiological tension, ranges from 69.9% to 94.6%. The intensity of humoral immunity  varied according to IgG titers in ELISA from 1: 100 – 1: 200 to 1:  3200 (rarely 1: 6400). The duration and intensity of immunity  depends on the number of vaccinations and the number of missed  remote revaccinations. Preservation and intensity of immunity with  reliability P = 95%, higher in persons vaccinated 6–10 times  compared with the group of vaccinated 3 times. In persons who had 4–8 booster dose of vaccine, the immunity persisted for 15–19–36 years with an IgG titer of not more than 1: 100. The neutralizing  activity of the sera of vaccinated individuals with antibody titers from 1:100 to 1: 6400 was studied for the Siberian subtype of BCE. The  degree of protection of the vaccinated population against the doses  of the virus found in individual mites is determined. From the doses  of the virus, 57% of the vaccinated population are most often found  in mites, and from the dose of 105– 8%. Recommendations are  proposed on the tactics of revaccination of the population, depending on the level of immunity.

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