In the period of 2000–2002 the authors examined antibodies in 143 persons, having been vaccinated with the FSME-Immun vaccine in the past, before the administration of 3rd to 6th dose of the vaccine against tick born encephalitis using the ELISA Immunozym set. One hundred and sixteen of them were subsequently examined after the vaccination with the Encepur vaccine. In the group of younger individuals the pre-vaccination level higher than 126 VIEU/ml was determined in 70.6–100% of subjects, the range in the older persons being 33.3–90.5%. Post-vaccination antibodies higher than 126 VIEU/ml were in 100%of younger and 92.6–100% of older vaccinated persons. Based on the results obtained it seems possible to recommend combination of vaccination with both available vaccines. It is necessary, however, to observe the three-year interval for re-vaccination.

        Key words: tick born encephalitis, vaccination, immunogenicity.