[Immunological structure of the population following the extermination of ticks in a natural focus of tick-borne encephalitis].

Ten years after the break of the chain of transmission of tick-borne encephalitis virus the level of the immune stratum of the local population declined from 59% to 39%. A decrease in the number of seroconversions was found in all the age groups but was particularly noticeable in the rural residents aged 10-30 years (39% and 13%), the mean titres declining from 1.8 log2 to 0.6 log2. In the rural residents over 30 years of age the immune stratum declined from 71% to 54%, the mean antibody titres from 3.4 to 2.5 log2. In subjects repeatedly infected in the natural focus, antihemagglutinins persisted for 10 years (the observation period).