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

Abstract

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.Goalof 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.

Influence exerted by biological and social risk factors on morbidity with tick-borne en-cephalitis in some regins in the Urals Federal District

“…In Kurgan region on average over 11 years only 69 thousand people were vaccinated and it amounted to 7.6 % of the overall region population; probably, insufficient vaccination and small scopes of immune prevention (only 39 % of all the people who had been bitten by ticks got immunoglobulin) [20] result in annual high morbidity with the disease among population and, consequently, in a growth in a share of people who fall sick after being bitten by ticks 2 . Low number of population vaccinated against the disease and violations in accomplishing official vaccination schemes can lead to a decrease in immunity against TBE in the nearest future and make effects produced by vaccination more remote [21].…”

Influence Exerted by Biological and Social Risk Factors on Morbidity With Tick-Borne E Ncephalitis in Some Regins in the Urals Federal District

“…Вероятно, недостаточные меры по вакцинации (в среднем за 11 лет на территории вакцинировано около 69 тысяч человек, что составило 7,6 % населения) и использовании серопрофилактики (противоклещевой иммуноглобулин получили лишь 39 % от числа пострадавших) в Курганской области [20] приводят к ежегодным высоким показателям заболеваемости населения и, следовательно, к росту доли заболевших среди лиц, пострадавших от укусов клещей 2 . Низкий охват населения профилактическими прививками и нарушения в официальных схемах вакцинации в ближайший временной период могут привести к снижению иммунитета против КВЭ и отсрочить эффект вакцинопрофилактики [21].…”